Download 3.3 Momentum and Energy Review

Mr. Wolf
Physics 1
Name: ______________________
Date: ______
Work, Power, Energy, and Momentum Review
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Define the following Terms:
o Newton’s 3rd
o Inelastic
o Energy
Law
Collision
o Potential
o Momentum
o Work
Energy
o Impulse
o Joule
o Kinetic
o Elastic
o Power
Energy
Collision
o Watt
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
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.)
6. A machine that uses 200 watts of power moves an object a distance of 15 meters in 25
seconds. Find the force needed and the work done by this machine.
Energy: Pontential and Kinetic CHOOSE ANY 3
7. 5. 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 1,000.0
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 beyour speed 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 velocity of an 500-kilogram elevator that has 4,000 joules of energy?
12. What is the mass of an object that creates 33,750 joules of energy by traveling at 30
m/sec?
Collisions: Consevation of Momentum CHOOSE ANY 2
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.” What is the result of this tackle?
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. How fast does the bull run with Tex
aboard?
15. Identical twins Kate and Karen are rowing their boat on a hot Summer afternoon when
they decide to go for a swim. Kate, whose mass is 45 kilograms, jumps off the front of
the boat at a speed of 3.00 m/sec. Karen jumps off the back at a speed of 4.00 m/sec. If
the 70-kilogram rowboat is moving at 1.00m/s when the girls jump, what is the speed of
the rowboat after the girls jump?
16. A 0.10-kilogram piece of modeling clay is tossed at a motionless 0.10-kilogram block of
wood and sticks. The block slides across a frictionless table at 15 m/sec.
a. At what speed was the clay tossed?
b. The clay is replaced with a “bouncy” ball tossed with the same speed. The
bouncy ball rebounds from the wooden block at a speed of 10 meters per
second. What effect does this have on the wooden block? Why?
Conservation of Energy: DO ALL THREE
17. 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?
18. A mass of 1,000 kilograms of water drops 10.0 meters down a waterfall every second.
a. How much potential energy is converted into kinetic energy every second?
b. What is the power of the waterfall in watts and in horsepower
19. 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. What is the power of the flashlight
bulb? Assume all of the energy in the batteries is used.