Download 41Work and E TEST - Mr-Hubeny

Do Not Write on Test!
Work and Energy- Answer all questions on White lined paper!
MULTIPLE CHOICE (2pts each= 30pts total)
.
1. In which of the following sentences is work done according to Physics?
a. Holding a heavy box requires a lot of work.
b. A scientist “works” on an experiment in the laboratory.
c. Sam and Rachel pushed hard, but they could not move the car.
d. John used a 20N force to lift a weight 2 meters.
2. In which of the following is not an example of work?
a. You push a box with a force a distance of 3 meters.
b. Mike pushes on the wall really hard but the wall doesn’t move..
c. Sam and Rachel push a car to the gas station.
d. You lift a bag of groceries onto the kitchen counter.
3. A force does work on an object if a component of the force
a. is in the opposite direction to the movement of the object.
b. is in the same direction to the movement of the object.
c. does not cause the object to move.
d. forces cannot cause work to occur.
4. Work is done when
a. the forces causes the object to move.
b. the force does not cause the object to move.
c. the force is zero.
d. the force and object movement are opposite each other.
5.. In which of the following scenarios is work done?
a. A weightlifter holds a barbell overhead for 2.5 s.
b. A construction worker lifts a heavy beam.
c. A car is parked on a hill.
d. A pencil is at rest on a desk top.
6. What happens to the Potential Energy and Kinetic energy of an ball as it rolls faster
down a hill?
a. The P.E. increases and the K.E. decreases
c. Both P.E. and K.E. decrease
b. The P.E. decreases and the K.E. increases
d. Both the P.E. and K.E. increase
7. Which of the following energy forms is associated with an object in motion?
a. potential energy
c. nonmechanical energy
b. nuclear energy
d. kinetic energy
8. Which of the following energy forms is associqted with an object sitting on top of a
ladder?
a. kinetic energy
c. potential energy
b. chemical energy
d. nuclear energy
9. The main difference between kinetic energy and potential energy is that
a. kinetic energy involves position, and potential energy involves motion.
b. kinetic energy involves motion, and potential energy involves position.
c. although both energies involve motion, only kinetic energy involves position.
d. although both energies involve position, only potential energy involves
motion.
10. Which form or forms of energy are involved in a rollercoaster ride?
a. kinetic energy
c. potential energy
b. both potential and kinetic energy
d. neither potential or kinetic energy
11. As a object falls its potential energy
a. decreases
b. increases
c. remains the same.
d. gets scared.
12.. What are the units for work and energy?
a. N
b. m
c. J
d. Watts
`13. Which of the following is a true statement about the conservation of energy?
a. Energy changes forms but the total energy will never be the same amount.
b. Energy changes forms but the total energy must always be the same amount
c. Energy will always be the same amount and can never change forms
d. I have less total energy now than when I first started this quiz.
14. Friction converts kinetic energy to
a. heat.
b. potential energy.
c. electrical energy.
d. hubeny energy.
15.. A more powerful motor can do
a. more work in a longer time interval.
b. the same work in a shorter time interval.
c. less work in a longer time interval.
d. the same work in a longer time interval.
CALCULATIONS (3 pts each = 15pts total)
Formulas:
F =ma
g = 10m/s2
W =Fd
P = W/t
PE = mgh
KE = 1/2mv2
16. Henry pushes a grocery cart with a force of 15N and moves the cart in the direction of the for
a total distance of 10? What is the total work that Henry did?
17. Jack and Jill lift a 4kg bucket of water to a height of 3m. Calculate the amount of work
that Jack and Jill did!
18. A person is using a force of 200 N to push a box. How much power does the person need
to push the box a distance of 4 m in 10 s?
19. How much potential energy does a 1000kg rollercoaster have when it is at the maximum
height of the tallest hill, which happens to be 90 meters high?
20. How much kinetic energy does a 1000kg rollercoaster have when it is traveling at its
maximum velocity at the bottom of the hill of 42m/s?
OPEN RESPONSE (5pts each, total = 10pts)
21. Two athletes are lifting weights. Athlete X lifts 445 N a distance of 2 m in 4 s. Athlete Y
lifts 445 N a distance of 2 m in 1 s. Assume that each athlete lifts the weights over his head
the same distance from the floor.
a. Calculate and compare the amount of work each athlete does. Show your calculations
and include units in your answer.
b. Calculate and compare the power each athlete uses. Show your calculations and
include units in your answer.
22. Students in a physics class are studying the energy changes that objects experience as
they fall. The students plan to drop a metal sphere with a mass of 0.05 kg from a height of
20.0 m onto a bed of sand. They predicted the results shown in the table below.
Time (s) Speed (m/s) Distance Fallen (m) Height (m)
0.0
0
0.0
20.0
0.5
5
1.3
18.7
1.0
10
5.0
15.0
1.5
15
11.3
8.7
2.0
20
20.0
0.0
1. Using the predicted values in the table, calculate the kinetic energy of the sphere just
before it contacts the sand at 2.0 s. Show your calculations and include units in your
answer.
2. Using the predicted values in the table, calculate the gravitational potential energy
at 0.0 s. Show your calculations and include units in your answer.
3. Describe what happens to the gravitational potential energy and the kinetic energy
as the sphere falls.
4. Assuming the students performed their calculations correctly, explain one possible
reason why they would find that the total P.E. of the sphere at its maximum height
did not equal the exact same amount of the K.E. of the sphere at its maximum speed.