2/28/12 - 6th Grade Concept & Modern Cars Design Critique

Guys,

Today we reviewed for the test that is tomorrow and you guys seem ready.  The second part of class we looked at concept and modern car designs -- at least one that has been made within the last 5 years.  By the end of class you should have picked out one car design you think is a good and one that is bad.  The assignment is posted on the homework site as well as the rubric so you guys have more clarification.  As we discussed in class, what I am looking for includes...

1. A photo of each car you have decided to critique
2. The specifications of each car such as length, weight, and gas mileage.
3. Your reason as to why each car has a good/bad car design using what you have learned from your experience with car design using the K'NEX pieces
4. A comparison and contrast of the two cars.

It was mentioned in class that some people would like to use a Venn diagram to compare and contrast the two cars and I am fine with that, whatever you feel comfortable doing.  I have posted a Venn diagram template on the homework site as well that you can use to complete this aspect of the task.

Tomorrow I will pick two cars to critique so you have an idea of what it should look like.  Study hard for your test and see you tomorrow.

2/28/12 - 8th Grade Review for Chemistry Final

Guys, below is the link to the Jeopardy game we played in class today for you to use to practice.

   - Jeopardy

I would suggest that you guys review old tests, worksheets, and skim the book to find the answers to the review worksheet.  Tomorrow will be the last time you will have a chance to ask any questions about material you do not understand.  I have posted the study guide on the homework site if you need another copy of it.  Happy studying, see you tomorrow.

2/27/12 - 8th Grade Cabbage Juice Indicator Experiment

Today we did an experiment where we used cabbage juice an indicator to tell us whether a substance was either an acid or base.

Photo courtesy of www.chemistryland.com

This lab went relatively well I thought, but I would just like to point out that there were no neutral substances being tested.  Some of the groups thought hydrogen peroxide was neutral because it was purple but the shade of purple was different than that of the cabbage juice.  Since it is only a slightly different color purple this means that hydrogen peroxide is ever so slightly acidic.

Today's lab should have showed you the wide range of pH levels found in everyday household items.  Below is a diagram of the pH scale using the colors of the cabbage juice to let you see the approximate pH of each substance.  This scale is a bit better than the one I showed in class today.

Photo courtesy of http://braukaiser.com

Tomorrow and Wednesday we will be reviewing a lot of material in order to prepare you for your cumulative chemistry final on Thursday and Friday.  There is a lot of material to cover and it would be helpful if you brought in all your old tests and handouts so we can go over any questions you might have on the material.  

2/27/12 - 6th Grade Review

Guys,

Today we read about Newton's 2nd and 3rd Laws of Motion.  A lot of the information has been covered already  but to highlight some of the important things from today.

Newton's 2nd Law - Force = Mass x Acceleration or as we have been saying Force is for your MAMA. This is a great way to see the relationship that exists between force, mass, and acceleration.


Gravity - The force that exists between two objects.  It depends purely on the MASS of the two objects and the DISTANCE APART those two objects are.  The image below gives you a good idea of what this  means.

Image courtesy of http://mail.colonial.net

Mass - The amount of "stuff" an object has.

Weight - The force of gravity acting on the mass of an object.

Newton's 3rd Law - For every action there is an EQUAL and OPPOSITE reaction.  

Equal and Opposite

Photo courtesy of www.wikipedia.org

We learned that although these forces are equal and opposite, they do not always cancel each other out.  Mass of the two objects plays a big part of which objects feels more of the force.  Take the example of hammering a nail into a wall.  The forces are equal and opposite but the nail goes into the wall an there is very little kick back from the force of the nail on the hammer.  This is because the mass of the hammer is much greater than that of the nail.

Photo courtesy of www.ipodphysics.com

I handed out a review sheet that I have posted on the homework site for those of you who might have been absent.  Nothing is officially due tomorrow but I would advise you to try and get most of the worksheet done so I can answer any questions you might have on anything.  Your test is on Wednesday so tomorrow will be the last chance to clear up anything that is still confusing.

2/24/12 - 8th grade notes

The wonderful world of Acids & Bases

Photo courtesy of www.wikipedia.org

           Characteristics of Acids


- Tastes sour
- React with metals & carbonates
- Turn blue litmus paper red
- Produce Hydrogen ions (+) when mixed with water
- Fall anywhere between 0 - 6.9 on the pH scale

Photo courtesy of www.apartmenttherapy.com

Characteristics of Bases


- Tastes bitter
- Do not react with metals or carbonates
- Turn red litmus paper Blue
- Produce Hydroxide ions (-) when mixed with water
- Fall anywhere between 7.1 - 14 on the pH scale

It is important to understand that when an acid or base reacts with water different things happen.  The pH scale literally means potential of Hydrogen so the acids have a much higher potential then the bases.  It is the amount of Hydrogen ions that make acids acids and bases bases.  


The strength of acids and bases depend on where it falls on the pH scale.  Hydrochloric acid is very strong, meaning it has a pH closer to 0.  Citric acid on the other hand is quite weak (because we actually ingest this acid) and it is closer to 7 on the pH scale.  The same goes for bases.  Drain cleaner is a very strong base that is closer to 14 while ammonia will irritate your hands but it is a relatively weak base with a pH closer to 7.


Below is a diagram of a pH scale.  Remember that the pH scale is actually logarithm (1 x 10  ^{- x}) where an acid with the pH of 1 will have .1 hydrogen atoms while a base with a pH of 13 will have .0000000000001 hydrogen atoms.

Image courtesy of http://richardanderson.me.uk

When a solution has a pH of 7 it is said to be Neutral.  Distilled water has a pH of 7.  It is interesting when you mix an acid together with a base of the same strength they will neutralize each other much like the sodium hydroxide and hydrochloric acid demonstration I did in class.

    - Video of an acid/base neutralization reaction

The video explains, as I did in class, that the byproducts of an acid and base neutralization are water and a salt.  Salt is a generic term used in chemistry to refer to an ionic compound that is made from a neutralization of an acid and base.  

2/24/12 6th Grade Notes - Newton's 1st Law Review

Guys,

Today we looked at Newton's 1st reading packet again.  Some important things we discussed were...
      - definition of force
      - what net force is
      - the difference between balanced/unbalanced forces
      - Newton's 1st law of motion
      - the different types of friction

Force - This is either a push or pull of an object.  It is always measured in Newtons (N) after Sir Isaac Newton.
Net Force - This is the combination of all the forces acting on A SINGLE object.  Look at the diagrams below to better understand net forces.

In the diagrams below, the one on the left, you would subtract to the two forces because they are in opposite directions giving you a net force = 0.  These are also called balanced forces.

In the middle diagram, since both forces are going in the same direction you add them together so the total force on the box is 10 Newtons.  This is also called a unbalanced force.

In the diagram on the right, the two forces are in opposite directions so you subtract them to find the total force acting on the object, which is 2 Newtons.  Since this is an unbalanced force and there is more force going right, the block will move in that direction.

  Net Force = 0 N              Net Force = 10 N          Net Force = 2 N

Newton's 1st Law of Motion

Once again, Newton's 1st Law states -
       An object in motion stays in motion while an object at rest will stay at rest unless acted upon by an outside force.

Photo courtesy of http://gvc.gvsd.ca

Looking at the motorcycle rider above, he clearly illustrates what Newton was talking about.  His body continues to move forward while his bike was acted upon by another force (the wall).

Friction is a force that is present everywhere in the world around us.  It is the force that acts against the object in motion to make it come to a stop.  This force is always OPPOSITE the direction in which the object is moving.

We learned that there are 3 types of friction...
Static - When an object is at rest and this is the force that you must use to have it begin moving.  It is the greatest of the friction forces.  Ex. Moving a refrigerator requires a lot of force to get it to start moving.

Photo courtesy of www.coppengerfamily.com

Sliding - When an object is moving (sliding) and it is the force that will cause the object to stop.  The key to this type of friction is that the object is already moving but only slightly because it is sliding.  It is the medium type of friction force.  Ex. A book on a desk will come to rest shortly after you have stopped pushing it.

Image courtesy of www.tutorvista.com

Rolling  - When an object is moving (rolling) and it is the force that will make it come to a stop.  This object is moving and circular in shape which allows this type of friction to be the lowest type of friction force.  Ex. A bike will come to rest after you stop pedalling but it will take much longer than the book to stop with sliding friction.

Photo courtesy of http://ummascorner.blogspot.com

2/23/12 - 8th grade notes

It is apparent to me now that all you guys in both classes know how to find the concentration of a solution so we moved on to solubility and what factors can affect it.

First, let's define solubility...Solubility is the measure of how well a solute can be dissolved in a solvent at a given temperature.  We discussed that the solubility of every solute is different and this is can be used to determine what the solute is without tasting it, which we would never do in an experiment.

Key Terms
Saturated solution - When a solution contains as much solute as the solvent can dissolve at a certain temperature.
Unsaturated solution - When a solution does not hold as much of a solute as possible at a given temperature.  For example, if you put salt in a solution and it dissolves and you can add more salt to the solution and it will dissolve then the solution is said to be unsaturated.
Supersaturated solution - When more solute has been dissolved in a solution at a given temperature.  When this solution is cooled down it is in a very unstable state so any disturbance will cause the extra solute in the solution to crystallize.  This link below is a really cool example of when a super saturated solution of sodium acetate trihydrate is cooled and then disturbed.

     - Sodium Acetate Trihydrate supersaturated solution
Disclaimer - I tried doing this several times at home with homemade stuff and did not work out so I am sorry you did not have the experience of seeing it first hand.

We looked at a solubility graph (above) of potassium nitrate and discovered that the line represents our saturation point at a given temperature and amount of potassium nitrate.  Any point above the line would be considered a supersaturated solution while any solution under the line would be an unsaturated solution.

There are three things that can change the solubility of a substance and they are Temperature, Pressure, and Type of solvent.


Temperature - When the temperature of a solvent goes up the solubility of a solid solute goes UP while the solubility of a gas solute goes DOWN.


Pressure - Affects the solubility of gases, something called Henry's Law.  It states that as pressure becomes greater, the solubility of a gas becomes greater.  The example we talked about in class dealt with SCUBA diving and the bends.  Below is a cool video that explains why whales don't get the bends by the company called Naked Science Scrapbook.

         - Why whales don't get the bends

Type of solvent - This is the last thing that affect solubility and the term "like dissolves like" is usually the way people refer to it.  "Like dissolves like" means that polar solutions will dissolve other polar solutions just as non-polar solutions will dissolve non-polar solutions.  A good example of this in action is olive oil and vinegar.  There is water in vinegar which is polar while oil is non-polar so therefore these two solutions will never stay mixed.

Here is a link to the sweet rap I told you about, it is a great review of what we covered over the last few days.  Time to get down with...The Solubility Rap!

We began to talk about Acids and Bases and we will cover them in more details tomorrow.  See you then.

2/22/12 - 8th Grade Notes

Only the second period class has homework tonight which is to complete the worksheet that deals with solving the concentration of a solution.  I decided to assign this because we were unable to complete an exit slip due to the fire drill.

Here are some helpful notes about what we covered in class today.

We were reminded of two key words when it comes concentration.  Those are dilute and concentrate.  There is a more detailed description of these words in an earlier post but basically a dilute when the  concentration of a solution is less than 50% and a concentrate is when a solution has more than 50% of a solute within it.

Here is the question that we spent a lot of time on today - How do I solve a concentration problem?

First a foremost, you all should remember the ratio that we set up in class today that will guide us through these problems.  As we found out in class sometimes it is not necessary to use the percentage but rather the other side could be used to find out how much of a solute is needed in a larger amount of solution as well.  The ratio is listed below...


                   Solute      =      % (concentrate) in solution
        Solvent                               100


There are a few things that must be remembered when using the above formula
                - Solute is always the smaller of the two in the solution and usually going to be the smaller number, usually given in g, mL, or L
                - Solvent refers to the total amount of the solution.  Key words that will help you identify this number is ___ of solution or sample.
                - When using a percentage of concentrate in a solution you always put the amount of concentrate over 100 because percentage is always measured on a scale up to 100.  If not given concentrate percentage or asked for it, DO NOT USE THIS RATIO.

Here is a practice problem - What is the percentage of concentrate of a 450 mL solution that has a 35 g of salt dissolved within it.

First you decided what information you are given within the problem.  Since the problem says 450 mL solution, I know that this is referring to the solvent.  That would mean the smaller number 35 g would be the solute in the solution.  Plug those figures in the ratio and you get...

                  35 g      =      %(concentrate) in solution
                450 mL                          100


Now you cross multiple to get the % of the solution by itself, which looks like this...

                  35 (100)       =          450 (% [concentrate] in solution)

Now you divide each side by 450, which looks like...

                                           3500            =     % (concentrate) in solution
                                            450 

That gives you the answer...

                               7.78 %      =   concentrate in solution

Always remember that you must include the unit of measure so in this problem it is asking for the concentrate so the unit is percentage.

2/22/12 - 6th grade

Guys,

Sorry in advance but I can never remember what class is which. 


Tomorrow, the first class (3rd period) will be continuing testing their 2nd modification tomorrow. By the end, of class every group will have finished with second test and will be working on completing the worksheet in class.

The second class (5th period) is completing the worksheet for homework because we finished testing our 2nd modifications in class. All groups should have run at least two tests (1st and 2nd modifications) with their cars and have that data on their worksheets along with sketches of each modification and their group's reasons for making those modifications.

See you tomorrow.

2/21/12 - 6th grade notes

Today we got a little farther along with our K'NEX car experience.  We will be done with this activity in the next few days so make sure you bring your worksheet to class because on the last day you will turn it in for a grade.

The first class almost got done with their 2nd build of the car of their choice from the booklet.  Tomorrow, those who have finished their car will test it and once again record the distance and time of their car.  Those groups that have not finished their cars will do so at the beginning of the period and test it in the hallway.  When each group has finished with their first test, they will make a small modification to their car and write down the justification for this decision.  The group will also sketch this new design before they are allowed to make the change and test.


The second class has already tested their newly designed cars down the ramp.  Because of the many types of cars groups choose, there was a lot of variation in what each group found.  Tomorrow, we will finished testing the second modification and complete the worksheet.  PLEASE BRING WORKSHEET TO CLASS! 

2/17/12 - 8th Grade Notes

Today we made ice cream so if you missed class you missed out.  The experience of making ice cream showed us many things about freezing point depression.  Through our experiment we learned that when you add a solute to a solvent you lower the freezing point and increase the boiling point.  Two example of this are when we put salt on sidewalks to prevent ice freezing on them (freezing point depression) and adding salt to water (increasing the boiling temperature of water) to cook pasta faster.

Try this link if you missed the experiment or want to try some more at home.
      - Boiling point and freezing point depression experiment

After our little activity we began to learn about concentration and dilutes.  The following terms are important...

concentrate - more solute is dissolved into the solvent.  You can usually tell if it is dark in color.  Ex.  Think about a concentrated juices at the grocery store or the maple syrup example we used in class.

Photo courtesy of www.maplecommunity.com

dilute - less solute is dissolved into the solvent.  This is usually apparent if the mixture is lighter in color.  Things are often diluted when you add more solvent to the solution.  The image below illustrates this point.

Image courtesy of http://water.me.vccs.edu

On Tuesday we will learn how to calculate the concentration of a solution and learn about solubility or certain solutes.  Solubility refers to how well something (the solute) dissolves (in the solvent).  Have a nice weekend!

2/17/12 - 6th Grade Science Notes

Guys,

Today we looked at graphing distance over time for the entire class.  Each group plotted their points on the graph and we were able to see that although the car were similar some outperformed others.  Below is a graph of each group's car average distance and time over the three trials.

In class we discussed some reasons that some cars worked better and what could have affected the each car's performance.  Some suggestions were...

        - too much friction between the wheels

        - too much drag (or wind friction) on the car

        - poor construction of car 

Some of the things we said could make our car's better were increasing the mass of the car because as we learned last week F = MA and if the mass increases, so will the acceleration and hopefully the car will go further.  Making a more aerodynamic car would be beneficial as well.

For homework you must do the three things listed below

- Find the average distance and time of the whole class data below (two blog posts ago) 

- Graph the class average and your team's car average on one graph. Please draw a line to represent the speed of your car from the 0,0 mark to the points on the graph like I did in class. 

- Write down how your car did compared to the class's average and why you think it performed that way. Also include the modifications your team plans to make to your car and why.

On the homework site there is a PDF that is blank graph paper.  Have a great weekend and see you Tuesday.

2/16/12 - 6th Grade

Guys,

Today we looked at graphing distance over time for the entire class.  Each group plotted their points on the graph and we were able to see that although the car were similar some outperformed others.  Below is a graph of each group's car average distance and time over the three trials.

In class we discussed some reasons that some cars worked better and what could have affected the each car's performance.  Some suggestions were...

        - too much friction between the wheels

        - too much drag (or wind friction) on the car

        - poor construction of car - different size wheels on each side of the car

Some of the things we said could make our car's better were increasing the mass of the car because as we learned last week F = MA and if the mass increases, so will the acceleration and hopefully the car will go further.  Making a more aerodynamic car would be beneficial as well.

For homework you must do the three things listed below

- Find the average distance and time of the whole class data below 

- Graph the class average and your team's car average on one graph. Please draw a line to represent the speed of your car from the 0,0 mark to the points on the graph like I did in class. 

- Write down how your car did compared to the class's average and why you think it performed that way. Also include the modifications your team plans to make to your car and why.

On the homework site there is a PDF that is blank graph paper.  Have a good night and see you tomorrow.

2/16/12 8th Grade Notes - Introduction to Mixtures

Everything in Chemistry deals with mixtures.  As we learned in class today, there are three main types of mixtures found in our world -- Suspensions, Colloids, and Solutions.  99 % of the mixtures that we deal with on a regular basis are solutions.

Key Terms
Solvent - The larger of the two in a mixture, it is often the one doing the "dissolving".  If you are at all unsure as to what is the solvent, water is a very solid guess as it is the universal solvent.
Solute - The smaller of the two in a mixture, it is the one that is dissolved in the solution.

Photo courtesy of http://media4.onsugar.com

               Suspension
A suspension is a mixture where the particles are large enough that they can be separated through filtration or settling.  The example the book gave was pepper in water and my example was chocolate milk.  No matter how much the pepper and water mixture is stirred, it will never mix together and is therefore uneven.  In my example the milk will mix with the chocolate but if we let the mixture sit for long enough the chocolate will settle at the bottom of the glass, which is so frustrating.

 Colloid

A colloid is where the particles are slightly smaller than those in a suspension and are mixed uniformly together.  The particles in the mixture are undissolved but do not settle like in a suspension.  Some example of a colloid are smoke, fog, milk, and JELLO.  The way to tell if a mixture is a colloid or a solution is through the Tyndall Effect which is how the mixture affects a path of light.  I will talk more about this at the end of the blog. 

Liquid JELLO
Photo courtesy of www.sundaysugar.com

Fog at Golden Gate Bridge
Photo courtesy of kids.britannica.com

                   Solution

A solution is a mixture where the mixture is evenly distributed much like a colloid but the solute is dissolved in the solvent.  A solution can not be separated through filtration or settling but rather by boiling or evaporating the solvent.  An example that we used a lot in class was the mixture of salt and water. Below is a link showing how water dissolves salt to form a solution.  It is this polarity of water that makes it the universal solvent.

- Water dissolving salt 

Tyndall Effect - This is how scientists identify whether a mixture is a colloid or solution.  If a light beam is pointed through a solution it will not pass through it while on the other hand if the same light is shot at a colloid it will pass through it.  A good example uses a laser pointer.  If you point a laser pointer at a wall all you see on the wall is a dot and the beam of light is invisible.  If, however, you point that same laser pointer through fog, you are able to see the entire beam of light as well as the point on the wall.  See pictures below to for illustration.

Laser through air - solution
Photo courtesy of www.colorfullighting.net

Laser through fog - colloid
Photo courtesy of www.freaklasers.com

The chart that was put on the board at the end of the class below.

                              Suspension             Colloid               Solution

Particle size                   Large                                Medium                               Small

Separation            Through filtration/                     Does not                        Through boiling/ 

                                     settling                               separate                            evaporation

Appearance                 Cloudy                                Cloudy                                Clear

Tyndall Effect                Yes                                     Yes                                      No

Even/Uneven              Uneven                               Uneven                                Even

Here is a great video that sums up all we learned.  He uses a lot of language that is a little above what we have learned but it will make sense to you guys.  You can stop watching after the 10:20 mark.

-  Khan Academy - Suspensions, Colloids, and Solutions

2/15/12 - 6th grade data from K'NEX cars

Guys,

Today we tested our cars and in our groups we collected data from 3 trials. As a class we wrote down the average of all 3 trials for each group in a table. Please copy down this information or print out for class tomorrow. We will be constructing a distance over time graph tomorrow in class and discuss what we found out with our car designs and how we can make improvements on our designs. The tables are below for each class.

3rd period data 

	Time (s)	Distance (cm)
Group # 1	8.67	826.7
Group # 2	7.98	727.6
Group # 3	7.85	762
Group # 4	5.26	516
Group # 5	12.65	904.3
Group # 6	3.61	538.6
Group # 7	8.38	784.7
Group # 8	7.49	714.6
Group # 9	8.25	801.7
Group # 10	3.5	391
Group # 11	6.47	641

5th period data

	Time (s)	Distance (cm)
Group # 1	7.38	882.3
Group # 2	8.32	727
Group # 3	7	752.67
Group # 4	6.84	788.6
Group # 5	3.5	293.3
Group # 6	5.6	595.3
Group # 7	8.9	732
Group # 8	6.56	607.6
Group # 9	3.2	306
Group # 10	11.29	774
Group # 11	7.83	810

2/14/12 - Building K'NEX cars

Today in class we worked through building our K'NEX cars.  We worked in teams of two and three people to construct a car out of plastic pieces that we will test for the next day or two.  All of you did a fine job constructing the cars and looking forward to testing them tomorrow.  Here are the two views of the car that you should have written on your paper, so if you do not have this drawn, please do so tonight.

K'NEX side view

K'NEX top view

Tomorrow we are going to test our cars using the force of gravity to power them down a ramp.  We take three trials and measure the distance over the amount of time the car took to reach that distance.  Once every group has had a chance to test the cars, we will come together as a class and graph the results.

2/10/12 - Newton's 2nd Law and Video Recap

Hey there guys, hope you weekend is going well.  On Friday we read about Newton's 2nd Law.  For the most part most of you were able to tell me what it was referring to in your exit slip but for those of you who forgot, Newton's 2nd Law is....

                                     F = MA
or net Force equals Mass times Acceleration (just remember Force is for your mama).  This is relationship that Newton discovered that all objects are governed by.  If you think about the law it makes total sense.  Much like the example in class, it takes a lot more force to move a more massive thing, for example a full shopping cart is harder to move than a lighter shopping cart.  Try for yourself at the link below and see what you discover.  The second link is a great video explaining Newton's 2nd Law and I think you will get a lot out of it.

        - Push the shopping cart

       - Newton's 2nd Law Video

The video we watched in class brought to life all 3 of Newton's Laws of Motion.  There were a lot of examples of how these laws were used to design the rides at Walt Disney World.  Here are Newton's three laws written out again.

Image courtesy of Google Images

   Newton's 1st Law of Motion 


An object in motion will stay in motion and an object at rest will stay at rest unless acted upon by an outside force.


                                                          Newton's 2nd Law of Motion

Image courtesy of Google Images

            
           F = MA
The amount of force needed to move an object depends on its mass and acceleration.

Newton's 3rd Law of Motion

For every action there is an equal 

and opposite reaction.

Image courtesy of Google Images

2/9/12 - 6th Grade Notes

Guys, today we went over the homework and by looking at your work it really showed me that you guys seem to understand how to find either the speed, time, or distance using the formula s = d/t.  Just remember to always write down what you need to find out in the problem, and what the problem gives you and the rest is just --  Plug it in, plug it in!

I was unable to teach the second class but for the first class, I realize that I went a little too fast through Newton's Law with you so we will be working more with that later.  For now just try and remember the formula F = MA, or Force is for your MAma.  Below is the link that was not working today to the NPR radio broadcast that talks about the the physics of football.  I find it neat and very interesting.

-  http://www.npr.org/2012/02/03/146362928/the-physics-of-a-football-players-performance

If any of you want more information on F = MA, below is a link to Khan Academy where he explains it.  The language he uses is a bit above what I expect you know but I think he does a good job of explaining things so you should gain at least a bit of information from it.

- http://www.khanacademy.org/video/newton-s-second-law-of-motion?topic=physics

2/8/12 - 6th Grade Notes

Today we discussed a little more about Net Force and I think everyone is on the same page now and understands the total amount of force exerted on an object is the net force.  Also, the direction of the larger force is the direction the object will move.  Like we did in class today with the stick, the image below of people playing tug-o-war where there is equal force on each side is an example of a balanced with the net force = 0 N.

Photo courtesy of  http://www.tutorvista.com/content/science/science-i/force-laws-motion/balanced-unbalanced.php

The second part of class we looked at speed and how to go about calculating it when you are given certain information.  Below is an awesome website that has animations explaining a whole lot of things relating to Physics, this link deals with speed specifically.

- http://www.physicsclassroom.com/mmedia/kinema/trip.cfm

Just so everyone is on the same page - speed and velocity are sometime interchanged in Physics class.  The biggest difference to note is that velocity just refers to speed in a certain direction.  The formula for calculating speed (or velocity) is...

When working through a problem you should always write down what you know and what you are trying to find.  Let's do 1 problem together - 

Ronny is going from their home to the Bears game at Soldier Field.  Ronny is walking at 3.55 km/hr and it takes him 2.5 hours to get to the game.  How far is soldier field from his house?

First we write down what we are trying to find.  Since "How far" is asking us a question about distance, that is what we will be solving for - D.

That then means that in the somewhere in the problem they must give us the speed and time.  Since we know that a measure of time is hours, 2.5 hr would be our time.  This leaves only 3.55 km/hr to be our speed.

Using that information - 3.55 km/hr = D / 2.5 hr.  To solve for D, we then multiply each side by 2.5 hr giving us the answer of 8.875 km.  

For homework, you are supposed to complete the five circled questions on the back of the worksheet.  See you tomorrow.

2/7/2012 - 6th Grade Notes

Sorry guys it took me so long to post these for you, my Internet at my place has been out all evening until right now.  Today we discussed about our lab with the rockets.

The rocket lab dealt with projectiles and we discovered that the angle the projectile is shot at will determine how far it will travel.  In the second class I gave the example of how I enjoy snowboarding and the angle of the jump will determine the flight of me off a jump.  In the picture below you will see what I am talking about.

Photo courtesy of ArisPhoto.com

This is exactly what happened in our experiment and we talked about how we would improve our experiment next time so that there would only be one variable, which would be length of the rocket.  If we made a machine or used a protractor to ensure that all rockets were launched at the same angle our test would be much more concrete.  

Another point was the amount of force each rocket was given and that could be better controlled by having the same person blow every rocket because it would give a better chance for the rockets to receive the same amount of force.  

Today we reviewed some terminology from before to make sure everyone is on the same page.  Some key terms include...

Mass - the amount of stuff there is of something.  

Force - this refers to a push or pull of an object.  Force is always referred to in Newtons and is always given a direction in which the force is acting.

Net force - this is the total amount of force acting on a single object.  So in the force diagram below the net force is zero because there is 5 N of force pulling from the left side and 5 N of force pulling from the right side, thus they cancel each other out. 

But when the net force does not equal zero like in the diagram below, the object will always move in the direction of the larger force.  So for this example the box will move to the right with a force of 2 N because it is being pulled in that direction with 2 N more force.

Speed - How fast something is traveling.  The formula for speed is S = d/t.  

Velocity is just the term for speed in a given direction.  For example, someone's speed would be 25 mph on Lake Shore Drive but that could easily be turned into velocity by adding a direction so 25 mph North on Lake Shore Drive.  

Acceleration - This refers to the change in speed over time.  The formula for acceleration is A = change in velocity/t

We will cover more on acceleration tomorrow and go further into Newton's 2nd Law - F = MA.