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Energy Review
True/False
Indicate whether the sentence or statement is true or false.
____
1. The energy of a moving object is called kinetic energy.
____
2. Negative work means the force applied is opposite to the direction of the displacement.
____
3. Efficiency is the ratio of the energy required to operate a device to the useful energy provided by the device.
____
4. The formula for power is P = (E )(
____
5. If the doubling time is 5 a, then the growth rate of energy consumption must be 20%.
____
6. Daylight savings time is applied in this country so that, in general, our waking hours are spent in daylight
requiring less energy to be used for such things as light.
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____
____
____
____
____
____
7. A bungee jumper is about to jump from a bridge and he hopes the elastic tied to his legs will not break as he
plummets downward. The type of energy at work when he is at the lowest point in his downward drop is
a. gravitational potential
d. elastic potential
b. kinetic
e. sound
c. thermal
8. The rapidness with which the atoms and molecules of a substance travel refers to
a. elastic potential energy
d. thermal energy
b. chemical potential
e. nuclear potential
c. electrical
9. The amount of work done to stop a bullet travelling through a tree trunk a distance of 50 cm with a force of 2.00
 102 N is
a. –4.00  102 J
d. –1.00  102 J
b. +4.00  102 J
e. +1.00  104 J
2
c. +1.00  10 J
10. A 55-kg person is skating on the Rideau Canal. She reaches a maximum speed and then glides to a stop in 100
m. The coefficient of friction between her skates and the ice is 0.010. What is the work done by the kinetic
friction?
a. –5.5  101 J
d. –5.5  105 J
b. –5.4  102 J
e. +5.4  102 J
1
c. +5.5  10 J
11. A construction worker does 450 J of work in lifting a load of bricks from the ground to a support stand 1.50 m
from the ground. What was the mass of the bricks she lifted?
a. 300 kg
d. 0.327 kg
b. 3.06 kg
e. 30.6 kg
c. 68.9 kg
12. A cheerleader is thrown vertically upward into the air. As the cheerleader rises, which one of the following
quantities increases?
a. gravitational potential energy
d. acceleration
b. speed
e. mechanical energy
c. kinetic energy
____ 13. In the following figure, a 0.60-kg ball is about to fall to the step below.
The gravitational potential energy of the ball relative to the step is
a. 8.8  101 J
d. 3.0  100 J
1
b. 2.9  10 J
e. 5.9  101 J
0
c. 6.0  10 J
____ 14. A roller coaster has two vertical loops one after the other. The roller coaster has a speed of 7.00 m/s at the top of
the first loop with a height of 22.2 m. It then proceeds around the second vertical loop with a height of 15.0 m.
What is the speed of the roller coaster at the top of the second vertical loop?
a. 7.00 m/s
d. 9.24 m/s
b. 13.8 m/s
e. 11.2 m/s
c. 8.40 m/s
____ 15. Consider a pendulum bob consisting of two different masses. Mass 1 has a mass of X and mass 2 has a mass 6
times that of mass 1, or 6X. The bob made up of the two masses is pulled to a height h and released. At the
lowest point in the swing mass 2, falls off. Assuming there is no friction and the centre of mass is ignored, what
height will mass 1 return to when it swings back?
a. 6h
d.
b. h
c.
e. 7 h
____ 16. A force of 25.0 N is required to raise a 500-N load with a pulley system. When the rope is pulled 10.0 m, the
load is raised 0.200 m. The efficiency of this pulley is
a. 60.0%
d. 40.0%
b. 5.00%
e. 2.00%
c. 50.0%
____ 17. An electric hoist provides 2.5  103 W of power to lift a 170-kg sack vertically upwards in 2.5 seconds. To what
height has the sack been lifted?
a. 3.8  101 m
d. 1.7  105 m
0
b. 3.8  10 m
e. 1.7  106 m
c. 2.7  10–1 m
____ 18. Which of the following statements most accurately describes the graph below?
a.
b.
c.
d.
e.
Each person used more energy per day.
The rate of energy consumption has decreased over the years.
The energy being consumed is approximately half as much over the five years.
This society has become more technologically dependent.
The energy consumed per day has increased exponentially.
____ 19. If you were told that the rate of energy use per person is higher in the southern part of Canada than in the
northern part, you would assume that
a. Southern Canadians waste more energy than northern Canadians.
b. Southern Canadians use technologies that require more energy.
c. Northern Canadians use less energy to produce the crops they need.
d. Southern Canadians use energy to heat their homes in winter, but also cool their homes in
summer; however, northern Canadians only heat their homes in winter.
e. The cost of energy to northern Canadians is higher and, therefore, they must conserve
energy at a higher rate.
____ 20. A power generating station burns 100 kg of coal every second. Each kg of coal contains approximately 25 MJ of
chemical energy and the power station generates approximately 750 MJ of electricity. The efficiency of the
station is
a. 0.33%
d. 3.0%
b. 30%
e. 21%
c. 95%
____ 21. When forests are cut down to be used in the process of biomass energy, which of the following statements is
NOT true?
a. Recreational use of the area decreases due to the barren nature of the landscape.
b. Wildlife increases in number and diversity since more area is provided.
c. If the clear-cutting occurs in a watershed area, then flooding could easily result.
d. Water pollution increases because trees have been removed from the ecosystem and there is
nothing there to stop water from flowing down a hill in a watershed.
e. The soil erodes and mudslides may result.
Short Answer
22. A grocery clerk applies a constant force and pulls a grocery cart at a constant velocity from a row of carts in a
period of time.
(a) Sketch a graph of the force applied as a function of the displacement.
(b) What does the area under the line represent?
23. You have two elastic bands of the same length; one is thin and the other is thick. Briefly explain how you could
test which elastic band would require more work to be done on it when stretched to the same displacement.
24. Give two reasons why a modern pole used for pole vaulting is more efficient than earlier bamboo poles.
25.
(a) List two advantages of continuing to use non-renewable resources.
(b) List two disadvantages of continuing to use non-renewable resources.
26. Under what conditions will a renewable resource become a non-renewable resource?
27. What three activities could you do to maintain Canada's renewable and non-renewable resources?
28. State if the following energy resources are available in your area and, if so, state where they may be located.
(a) geothermal
(b) nuclear
(c) hydraulic
(d) biomass
Problems
29. A soap box derby is about to start and Marisa pushes her 15.0-kg car to the start line 10.0 m up the hill.
Calculate the work done by Marisa on the soap box car over the 10.0 m if friction is ignored.
30. A 500.0-g bird has gathered a breakfast of 10 juicy worms for her young offspring. Each worm has a mass of
5.00 g and must be delivered to the waiting offspring 10.0 m up in the tree. Calculate the least amount of work
mother bird will have to do to feed breakfast to her little birds.
31. A 140-kg barrel that is initially at rest is pushed by a constant net force of 40.0 N. The barrel travels 200 cm in
5.0 s. The acceleration of the barrel is 0.25 m/s2. Calculate the increase in kinetic energy during the 5.0 s.
32. A 200.0 N force moves a 120.0-kg crate on a frictionless surface from rest to a final speed of 9.6 m/s. What is
the displacement of the crate at the time it reaches this speed?
33. Determine the heat lost when 140 kg of water cools from 45.0C to 15.0C.
(cw = 4.18  103 J/kg·C)
34. Find the specific heat capacity of a 24-kg substance whose temperature rises from 2C to 33C when 4.72  105
J of heat is added. Convert the answer to units of J/g·C.
35. A 65-kg student climbs a 40.0-m flight of stairs in 15.0 s. Calculate the
(a) gravitational potential energy at the top of the stairs.
(b) power of the climb.
36. An elevator motor provides 45.0 kW of power while lifting a 2000-kg elevator 35.0 m. If the elevator contains
six passengers of the same mass and it takes 20.0 s to accomplish this task, determine the mass of each
passenger.
37. Between 1980 and 2000, the world's population increased by 1.7%/a.
(a) Determine the doubling time.
(b) The population in 1980 was 4.5 billion, what was it in 2000?
Essay
38. State two types of renewable resources that could easily be used to supply some or all of a typical school's
energy supplies and explain why these resources are usually not used to supply the needed energy.
Energy Review
Answer Section
TRUE/FALSE
1.
2.
3.
4.
5.
6.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
T
T
F
F
F
T
REF:
REF:
REF:
REF:
REF:
REF:
K/U
K/U
K/U
K/U
K/U
MC
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
4.1
4.2
4.4
4.6
5.1
5.4
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
EW1.01
EW1.01
EW1.05
EW1.05
EW3.01
EW3.01
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
REF:
K/U
K/U
K/U
K/U
K/U
K/U
K/U
K/U
K/U
K/U
K/U
I
MC
K/U
MC
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
4.1
4.1
4.2
4.2
4.2
4.3
4.3
4.4
4.4
4.2, 4.4
4.6
5.1
5.1
5.2
5.3
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
LOC:
EW1.01
EW1.01
EW1.02
EW1.02
EW1.02
EW1.01, EW1.03
EW1.01, EW1.03
EW1.03
EW1.03
EW1.05
EW1.04
EW2.02
EW3.01
EW1.05
EW3.01
MULTIPLE CHOICE
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
D
D
D
B
E
A
E
B
B
D
B
E
B
B
B
SHORT ANSWER
22. ANS:
(a)
(b) The area under the line represents the work as in
area = l  w
work = force  displacement
REF: I
OBJ: 4.2
LOC: EW1.01, EW1.02
23. ANS:
• Hypothesize which elastic band will require more work performed on it.
• Use a newton meter to measure the force applied to each elastic band.
• Measure the same displacement of each elastic band with a ruler.
• Calculate the work done on each elastic band.
• Carry out experiment again to verify results.
• Draw a conclusion.
REF: C
OBJ: 4.2
LOC: EW1.02, EW1.03, EW2.01, EW2.03
24. ANS:
Modern pole vaulting poles are stronger, have a lower density, and are stiffer. (The student may choose any
two.) This results in more energy being used in lifting the vaulter and not lost to the twisting or bending of the
pole. More of the elastic energy is returned to the pole vaulter and, thus, the athlete is lifted higher.
REF: MC
25. ANS:
OBJ: 4.4
LOC: EW1.05, EW3.02
(a) (Any two of the following or any other reasonable answer.)
-economy already in place
-jobs would be maintained and maybe even increase in number
-allows industries to proceed with expansion in many areas
-non-renewable resources produce much more energy than renewable sources
(b) (Any two of the following or any other reasonable answer.)
-pollution
-increase in greenhouse effect
-health effects from pollution and environmental change
-resources will run out very soon and nothing will be there to replace them
REF: MC
OBJ: 5.3
LOC: EW3.01
26. ANS:
A renewable resource will become a non-renewable resource if it is mismanaged, such as clearcutting a forest
and not replanting enough trees or cutting down too many trees that will take centuries to grow back.
Environmental conditions may change in the future and that site may not provide that type of energy anymore.
For example, a geothermal fissure may close.
REF: MC
OBJ: 5.3
LOC: EW3.01
27. ANS:
(Any three of the following or any other reasonable answer.)
-Use water wisely and turn it off when not in use.
-Water plants and the lawn only when needed.
-Turn off lights and appliances when not in use.
-Buy energy efficient devices.
-Reuse, reduce, and recycle.
REF: MC
OBJ: 5.4
28. ANS:
Answers will vary depending on location.
LOC: EW3.01
REF:
MC
OBJ: 5.3
LOC: EW3.01
PROBLEM
29. ANS:
The work done by Marisa on the soap box car over the 10.0 m if friction is ignored is 1470 J.
REF: K/U
30. ANS:
OBJ: 4.2
LOC: EW1.02
The mother bird must do 5.39  101 J of work to deliver breakfast to her young.
REF: K/U
OBJ: 4.3
31. ANS:
m = 140 kg
Fnet = 40.0 N
d = 200 cm = 2.00 m
a = 0.25 m/s2
t = 5.0 s
LOC: EW1.01, EW1.03

The increase in kinetic energy during the 5.0 s is 7.0  101 J.
REF: K/U
32. ANS:
F = 2.00  102 N
m = 1.20  102 kg
v1 = 0 m/s
v2 = 9.6 m/s
d=?
OBJ: 4.3
LOC: EW1.03
The displacement of the crate at the time it reaches this speed is 2.8  101 m.
REF: K/U
OBJ: 4.3
33. ANS:
m = 140 kg
tinitial = 45.0C
tfinal = 15.0C
c = 4.18  103 J/kg·C
Qlost = ?
LOC: EW1.03
The heat lost is 1.76  104 J.
REF: K/U
34. ANS:
m = 24 kg
tinitial = 2C
tfinal = 33C
Qgained = 4.72  105 J
c=?
OBJ: 4.5
LOC: EW1.03
The specific heat capacity is 6.3 10–1 J/g·C.
REF: K/U
35. ANS:
OBJ: 4.5
LOC: EW1.03
(a)
The gravitational potential energy at the top of the stairs is 2.5  104 J.
(b)

The student's power for the climb is 1.7  103 W.
REF: K/U
OBJ: 4.6
36. ANS:
P = 45.0 kW = 4.5  104 W
mass of elevator (m1)= 2.00  103 kg
h = 35.0 m
t = 20.0 s
number of passengers = 6
mass of elevator and passengers (M) = ?
mass of each passenger (m2) = ?
Ep = Mgh
LOC: EW1.04
The mass of each passenger on the elevator was 1.03  102 kg.
REF: K/U
37. ANS:
OBJ: 4.6
LOC: EW1.04
(a)
The doubling time is approximately 42 a.
(b) (1.017)20 = 140%
140%  4.5 billion = 6.3 billion
The population in 2000 was 6.3 billion.
REF:
K/U
OBJ: 5.1
LOC: EW3.01
ESSAY
38. ANS:
Solar energy is a definite possibility for most schools. If the building is designed to maximize its usage of the
sun in heating up the building and devices are put in place to block out those rays in the summer, this could be a
cost-effective option in the long run. Solar power, though photocells, could generate electricity and supply it
directly into the power plant of the school. Building schools close to residential areas and with various facilities
is a priority. Unfortunately, location or orientation for passive solar heating is not a priority. Active solar power
usually requires a rewiring of the existing electrical system and a large area to install the large solar panels, so
expense is a factor in the start-up costs.
Wind energy could be employed in many areas with the use of a vertical axis generator. Again, a rewiring of the
existing electrical system would be needed and space would be required to install the wind generator. Initial
start-up costs would also be a factor.
Biomass energy, such as burning wood or animal wastes would be a possibility. Burning wood adds to the
pollution problem in the immediate area and the idea of burning animal wastes makes some people
uncomfortable as it may present certain health risks.
REF:
MC
OBJ: 5.4
LOC: EW3.01