SPH3U Exam Review

Work

1. The work done on a system is equal to

its change in:

A. force

B. energy

C. power

D. both B and C

Work

1. The work done on a system is equal to

its change in:

A. force

*B. energy

C. power

D. both B and C

Units

2. Energy may be measured in:

A. Joules

B. calories

C. kilowatt-hours

D. all of the above

Units

2. Energy may be measured in:

A. Joules

B. calories

C. kilowatt-hours

*D. all of the above

Total Mechanical Energy

3. An object is lifted to some height and

then dropped. While it is being lifted, its

total mechanical energy:

A. increases

B. decreases

C. remains the same

D. It cannot be determined.

Total Mechanical Energy

3. An object is lifted to some height and

then dropped. While it is being lifted, its

total mechanical energy:

*A. increases

B. decreases

C. remains the same

D. It cannot be determined.

Total Mechanical Energy

4. An object is lifted to some height and

then dropped. During the drop, its total

mechanical energy:

A. increases

B. decreases

C. remains the same

D. It cannot be determined.

Total Mechanical Energy

4. An object is lifted to some height and

then dropped. During the drop, its total

mechanical energy:

A. increases

B. decreases

*C. remains the same

D. It cannot be determined.

Work and Friction

5. A student uses a force of 20 N to push a book 1.0 m along a table. A frictional force of 20 N opposes the motion of the book. The work done by the student is:

A. 0 J

B. 20 J

C. 40 J

D. It cannot be determined.

Work and Friction

5. A student uses a force of 20 N to push a book 1.0 m along a table. A frictional force of 20 N opposes the motion of the book. The work done by the student is:

A. 0 J

*B. 20 J

C. 40 J

D. It cannot be determined.

Power

6. Machine A does 10 J of work in 1 s. Machine B does 10 J of work in 2 s. Which machine has the greatest power output?

A. Machine A

B. Machine B

C. Their outputs are the same.

D. It cannot be determined.

Power

6. Machine A does 10 J of work in 1 s. Machine B does 10 J of work in 2 s. Which machine has the greatest power output?

*A. Machine A

B. Machine B

C. Their outputs are the same.

D. It cannot be determined.

Efficiency

7. Machine C uses 2500 J of fuel energy to

do 500 J of useful work. Its efficiency is:

A. 0%

B. 20%

C. 100%

D. 500%

Efficiency

7. Machine C uses 2500 J of fuel energy to

do 500 J of useful work. Its efficiency is:

A. 0%

*B. 20%

C. 100%

D. 500%

Energy Loss

8. The 2000 J of energy lost in the

Question 7 was probably lost as ______

energy.

A. elastic potential

B. gravitational potential

C. heat

D. kinetic

Energy Loss

8. The 2000 J of energy lost in the

Question 7 was probably lost as ______

energy.

A. elastic potential

B. gravitational potential

*C. heat

D. kinetic

Heat Exchange

9. If 100 g of water at 100oC is added to a 50 g aluminum cup at 20oC:

A. The temperature change of the water will be the same as the temperature change of the cup.

B. The temperature change of the water will be less than the temperature change of the cup.

C. The temperature change of the water will be greater than the temperature change of the cup.

D. No transfer of heat energy will occur between the materials.

Heat Exchange

9. If 100 g of water at 100oC is added to a 50 g aluminum cup at 20oC:

A. The temperature change of the water will be the same as the temperature change of the cup.

*B. The temperature change of the water will be less than the temperature change of the cup.

C. The temperature change of the water will be greater than the temperature change of the cup.

D. No transfer of heat energy will occur between the materials.

Heat Transfer

10. Which of the following processes is

most effective at transferring heat

energy within fluids?

A. conduction

B. convection

C. radiation

D. all of the above

Heat Transfer

10. Which of the following processes is

most effective at transferring heat

energy within fluids?

A. conduction

*B. convection

C. radiation

D. all of the above

Energy Transformations

1. A textbook is dropped from some height

onto the floor. Explain, using energy

transformations, why and how the book

stops when it hits the floor.

Energy Transformations

1. A textbook is dropped from some height

onto the floor. Explain, using energy

transformations, why and how the book

stops when it hits the floor.

The floor does negative work on the book

by exerting a normal force opposite the

direction of motion.

Entropy

2. Explain what is meant by “entropy” and

how the concept applies to the

transformation of mechanical energy.

Entropy is the disorder of a system. As

energy is transferred, some is lost as

non-useful forms, so the entropy of the

system is increased.

Problem Solving 1

1. A student applies a force of magnitude

39.0 N at an angle of 22.6o with the

horizontal to push a 4.00-kg textbook

1.00 m across a table to a final speed of

1.75 m/s. Find the work done by friction

on the textbook.

Problem Solving 1

1. A student applies a force of magnitude

39.0 N at an angle of 22.6o with the

horizontal to push a 4.00-kg textbook

1.00 m across a table to a final speed of

1.75 m/s. Find the work done by friction

on the textbook.

JW

mNW

dFW

student

student

student

0.36

6.22cos)00.1)(0.39(

cos

Problem Solving 1

1. A student applies a force of magnitude

39.0 N at an angle of 22.6o with the

horizontal to push a 4.00-kg textbook

1.00 m across a table to a final speed of

1.75 m/s. Find the work done by friction

on the textbook.

JE

kgE

mvE

k

sm

k

k

125.6

)75.1)(00.4( 2

21

2

21

Problem Solving 1

1. A student applies a force of magnitude

39.0 N at an angle of 22.6o with the

horizontal to push a 4.00-kg textbook

1.00 m across a table to a final speed of

1.75 m/s. Find the work done by friction

on the textbook.

JW

JJW

WEWWWE

friction

friction

studentkfrictionfrictionstudentk

9.29

0.36125.6

Problem Solving 2

2. 3.0-kg parcels are lifted up to the top of

a 5.0-m high ramp. If 24 parcels are

lifted every minute, what power is

required to lift the parcels? If this power

is supplied by a 12 kW motor, what is

the efficiency of the motor?

Problem Solving 2

2. 3.0-kg parcels are lifted up to the top of

a 5.0-m high ramp. If 24 parcels are

lifted every minute, what power is

required to lift the parcels?

WP

s

mkgP

t

hmg

t

E

t

WP

s

m

8.58

60

)0.5)(8.9)(0.3(24 2

Problem Solving 2

2. 3.0-kg parcels are lifted up to the top of

a 5.0-m high ramp. If 24 parcels are

lifted every minute, what power is

required to lift the parcels?

WP

s

mkgP

t

hmg

t

E

t

WP

s

m

8.58

60

)0.5)(8.9)(0.3(24 2

Problem Solving 2

If this power is supplied by a 12 kW motor,

what is the efficiency of the motor?

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8.58or

W

Wefficiency

P

Pefficiency

in

out