Download Unit 9 Test Review – Work and Energy

Unit 9 Test Review – Work and Energy
Honors Physics
Be sure to study the following:
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Energy pie charts
Energy bar graphs/energy flow diagrams (Qualitative)
o Identify types of energy present
o Recognize energy transfer into/out of a system
Conservation of energy calculations
o Identify types of energy present (kinetic, GPE, EPE, chemical, thermal (Eint))
o Calculate how much of each type of energy is present in a particular situation
o Recognize when energy changes form or is transferred into/out of a system
o Apply calculations to these energy changes and transfers
Kinetic energy = ½ mv2
Gravitational potential energy = mgh
Elastic potential energy = ½ kx2
Work = E = Fx
Power = W/t = E/t
Practice Problems
1. Draw a series of energy pie charts for throwing a ball straight up in the air and catching it at the same level
from which it was thrown. Where is the ball moving the fastest?
2. You pull a wagon, initially at rest, until it reaches constant velocity, along a level sidewalk.
3. A 7500 kg 18-wheeler traveling at 20 m/s exits onto the runaway truck ramp on the freeway. When it comes
to a stop, it is 10 m higher than before. Complete the energy bar graph below. How much energy was
dissipated by friction?
For the following question, make quantitative comparisons, by determining the ratio called for in the question.
Show work or provide some argument for your answer.
4. Consider the diagram at left which shows two balls, A and B, which are
dropped from the same height. Ball B has twice the mass of ball A.
EgB
a. Determine the value of the ratio E
gA
VB
b. Determine the value of the ratio V at impact.
A
c. How does the acceleration of B compare to that of A?
5. A 50.0 kg diver steps off a diving board and drops straight down into the water. The water provides an
average net force of resistance of 1500 N to the diver’s fall. If the diver comes to rest 5.0 m below the water’s
surface, what is the total distance between the diving board and the diver’s stopping point underwater? (Hint:
Find the work done on the diver by the water. Remember, work is a change in energy.)
6. If you were to throw a 1 kg ball straight up in the air with an initial velocity of 6 m/s, how much kinetic
energy would the ball have initially? How much KE would it have after it has been in the air 0.5 seconds?
7. A 10 kg crate sits at the top of a frictionless hill with an incline of 25o. What is the kinetic energy of the
crate after it travels a distance of 3.5 m down the hill?
8. A boy pulls his sled across the snow by a rope that makes a 55o angle with the ground. If the boy pulls the
sled a distance of 12 m, how much work does he do on the sled?
9. Suppose W is the energy transferred stretching a spring from 0 to 0.10 m. The amount of work done
stretching the same spring from 0.10 m to 0.20 m is:
a. W
b. 2W
c. 3W
d. 4W
10. A 50.0 kg student climbs 5.00 m up a rope at a constant speed. If the student’s power output is 200.0 W,
how long does it take the student to climb the rope? How much work does the student do?