Momentum and Energy Review

This packet will cover all of the material for chapter 3 . YOU will be responsible for having this in class every day. Included in this packet are the note sheets, homework, and lab activities.

IF YOU MISS A CLASS PERIOD IT IS YOUR RESPONSIBILITY TO DETERMINE THE WORK ASSIGNED. Check the website, email MR. WOLF or a classmate.

Website: mrwolfteacher.com

Mr. Wolf’s email:

Assignment / Page # / Date due:
Finish Procedure and Data Table / 4
Review / 7-9
Important Vocabulary
Newton’s 3rd Law
Momentum
Impulse
Law of Conservation of Momentum / Work
Power
Joule
Watt
Kinetic Energy
Gravitational Potential Energy Conservation of Energy
Horsepower /





DO NOT LOSE THIS PACKET.

You will lose points if your have to get a new one.

This packet will be collected at the start of the weekly quiz on Friday ______.

Conservation of Momentum

Lab - Conservation of Energy

Is energy transformation from potential to kinetic 100%?

When the marble speeds up, it gains kinetic energy from falling down a hill. This kinetic energy is converted from the potential energy (the stored energy) the marble had at the top of the hill. As the marble travels, it trades potential and kinetic energy back and forth. This conversion of energy from one form to another is explained by the law of conservation of energy, which states that energy can be converted from one form to another but it cannot be created or lost. To measure the kinetic energy, you will use the photogate to find the speed of the marble. To calculate the potential energy, you need to measure the height.

Getting Started:

1.  The distance the marble moves while it is blocking the photogate beam is equal to the ______of the marble. It’s hard to measure this accurately, but it’s 0.021 meters.

2.  What’s the equation for calculating kinetic energy? Label what all the variables stand for.

3.  When the marble is at the top of the rollercoaster, before it is released, what kind of energy does it have?

4.  What’s the formula for calculating potential energy? Label what all the variables stand for.

5.  What does the law of conservation of energy tell you about the total energy of the marble as it rolls along the rollercoaster?

Procedure:

You task tonight is to write a procedure for the lab that you will do tomorrow in class. Mr. Wolf will demonstrate how to set up the track and equipment. TAKE NOTES during this. Your procedure should include:

·  Numbered steps

·  Detailed directions

·  Written for an audience of other 9th grade physics students. (So you can say something like “Assemble the track.)

·  Some helpful diagrams

·  You will only need 1 photogate and just move it along to different positions. Make sure that each time you reposition it that is it firmly attached. You should include this in your procedure.

Collecting data:

Find the kinetic and potential energy of the marble at each location along the rollercoaster.

When measuring POTENTIAL energy, measure the height of the bottom of the marble above the table surface. This will be a bit tricky when the marble is over the stand. In these locations, measure the height to the stand and add the height of the wood platform.

When measuring time to calculate KINETIC energy, make sure the photogate is pressed firmly against the bottom of the track and that it isn’t tilted.

You’ll need the mass of the marble. Mass in grams = ______Mass in kg = ______

You will need to create your own data table for this lab. In order to answer the question of this

lab, Is energy transformation from potential to kinetic 100%?, you will need to determine the total energy at several different point along the track. Think about the different variables you need in order to calculate each type of energy. Below is a list of the positions that you should measure the total energy at.

Position on coaster (cm) / 0 / 10 / 27 / 43 / 58 / 82 / 105 / 125
Description of location / Very top of 1st hill / Bottom of 1st hill

You will need to add different rows for variable that you will either measure or calculate. What are these other variables?

Graphing and Analyzing Data:

Answer the following on a separate sheet of paper (back of your data table) and staple to this sheet along with the graphs when you are finished.

A)  Get a piece of blank graph paper and turn it sideways so the long edge is along the bottom. Make a graph of energy (y-axis) vs. position on coaster (x-axis). You will have THREE lines (not exactly lines, more like curves) on this graph:

Total energy vs. position on coaster

Kinetic energy vs. position on coaster

Potential energy vs. position on coaster

Color code the lines and make a key on your graph. I suggest using pencil in case you make a mistake. Color it after you know it’s perfect. Make the graph extra beautiful!

B)  Describe what you notice about the potential energy and kinetic energy lines on the graph. How do they compare? Write a sentence or two.

C)  Describe what you notice about the total energy graph. Write several sentences. Is the total energy conserved? Why or why not?

Work, Power, Energy, and Momentum Review

You should be able to do the following for the quiz:

  Define and calculate potential and kinetic energy.

  Use the law of conservation of energy to explain what happens to KE and PE as an object falls or rises.

  Define and calculate work and power.

  Define and calculate momentum and impulse.

  Explain the difference between and inelastic collision and an elastic collision.

  Explain what it means to say that momentum is conserved in a collision. Use momentum conservation to calculate the speed of objects after a collision.

  Describe what happens in an elastic collision when objects have the same mass.

  Recognize that the FORCE IS THE SAME ON BOTH OBJECTS DURING A COLLISION and explain how the EFFECT of the force varies.

·  Define the following Terms:

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o  Newton’s 3rd Law

o  Momentum

o  Impulse

o  Elastic Collision

o  Inelastic Collision

o  Work

o  Joule

o  Power

o  Watt

o  Energy

o  Potential Energy

o  Kinetic Energy

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·  A toy gun shoots a dart.

o  How does the force on the gun compare to the force on the dart? Why?

o  The mass of the gun is greater than the mass of the dart. Which moves faster immediately after shooting, the gun or the dart? Explain why.

o  What do you know about the momentum of the gun compared to the momentum of the dart after the dart goes flying?

·  What happens to the kinetic energy of an object if you: (Be specific!!!)

o  Double the mass?

o  Double the velocity

o  Reduce the velocity by a third?

·  Describe what the conservation of energy is within the context of a roller coaster.

·  What are the formulas for: Impulse, momentum, work, power, PE and KE

Below are some practice problems. GIVEN / WANT / FORMULA / SOLVE

Work and Power CHOOSE ANY 3

1.  Nicholas spends 20 minutes ironing shirts with his 1,800-watt iron. How many joules of energy were used by the iron? (Hint: convert time to seconds).

2.  It take a clothes dryer 45 minutes to dry a load of towels. If the dryer uses 6,750,000 joules of energy to dry the towels, what is the power rating of the machine?

3.  A force of 100 newtons is used to move an object a distance of 15 meters with a power of 25 watts. Find the work done and the time it takes to do the work.

4.  If a small machine does 2,500 joules of work on an object to move it a distance of 100 meters in 10 seconds, what is the force needed to do the work? What is the power of the machine doing the work?

5.  A machine uses a force of 200 newtons to do 20,000 joules of work in 20 seconds. Find the distance the object moved and the power of the machine. (Hint: A joule is the same as a Newton-meter.)

  1. A machine that uses 200 watts of power moves an object a distance of 15 meters in 25 seconds. Find the work done by this machine and the force needed.

Energy: Pontential and Kinetic CHOOSE ANY 4

7.  Two objects were lifted by a machine. One object had a mass of 2 kilograms, and was lifted at a speed of 2 m/sec. The other had a mass of 4 kilograms and was lifted at a rate of 3 m/sec.

a.  Which object had more kinetic energy while it was being lifted?

b.  Which object had more potential energy when it was lifted to a distance of 10 meters? Show your calculation. (Remember that gravity = 10 m/sec2)

8.  You are on roller blades on top of a small hill. Your potential energy is equal to 1,000 joules. The last timeyou checked your mass was 60.0 kilograms.

a.  What is your weight in newtons?

b.  What is the height of the hill?

c.  If you start skating down this hill, your potential energy will be converted to kinetic energy. At thebottom of the hill, your kinetic energy will be equal to your potential energy at the top. What will be your kinetic energy at the bottom of the hill?

9.  Answer the following:

a.  What is the kinetic energy of a 1-kilogram ball is thrown into the air with an initial velocity of 30 m/sec?

b.  How much potential energy does the ball have when it reaches the top of its ascent?

c.  How high into the air did the ball travel?

10. What is the potential energy of a 3 kilogram-ball that is on the ground?

11. What is the kinetic energy of an 500-kilogram elevator that is moving at 4 m/s?

  1. What is the mass of an object that creates 33,750 joules of energy by traveling at 30 m/sec?

Collisions: Consevation of Momentum DO BOTH

13. Terry, a 70-kilogram tailback, runs through his offensive line at a speed of 7.0 m/sec. Jared, a 100-kilogram linebacker, running in the opposite direction at 6.0m/s, meets Jared head-on and “wraps him up.”

a.  What is the momentum of each player?

b.  What is the initial momentum of the system?

c.  What is the final momentum of the system?

d.  What is the final velocity of both tackled players?

14. Tex, an 85.0 kg rodeo bull rider is thrown from the bull after a short ride. The 520.0 kg bull chases after Tex at 13.0 m/sec. While running away at 3.00 m/sec, Tex jumps onto the back of the bull to avoid being trampled.

a.  What is the momentum of the bull and Tex?

b.  What is the initial momentum of the system?

c.  What is the final momentum of the system?

d.  How fast does the bull run with Tex aboard?

Conservation of Energy: DO BOTH

15. The power of a typical adult’s body over the course of a day is 100 watts. This means that 100 joules of energy from food are needed each second.

a.  An average apple contains 500,000 joules of energy. For how many seconds would an apple power a person?

b.  How many joules are needed each day?

c.  How many apples would a person need to eat to get enough energy for one day?

  1. An alkaline AA battery stores approximately 12,000 J of energy. A small flashlight uses two AA batteries and will produce light for 2 hours.

a.  What is the total energy in the flashlight?

b.  How long in seconds does it run for?

c.  What is the power of the flashlight bulb? Assume all of the energy in the batteries is used.

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Answers:

1.  2160000J

2.  2500W

3.  60 sec

4.  25 meters, 250 Watts

5.  100 meters,1000 Watts

6.  5000 J, 333 N

7.  the 4 kg one for both

8.  A) 600 N B) 1.6 m C) 1000 J

9.  450 J, 450 J, 45 m

10.  0 J

11.  400 J

12.  75 kg

a.  490 kgm/s and -600 kgm/s

b.  -110 kgm/s

c.  -110 kgm/s

d.  -0.65 kgm/s

a.  6760 kgm/s and 255 kgm/s

b.  7015 kgm/s

c.  7015 kgm/s

d.  11.6 m/s

a.  5000 seconds

b.  8640000 J

c.  17.3 apples

a.  24000 J

b.  120 seconds

c.  200 watt

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