Deck 13: Energy and Power

Question 1

In the absence of heat transfer, and assuming negligible losses and no work, conservation of mechanical energy states that the total mechanical energy of a system is

A) increasing
B) constant
C) decreasing
D) decreasing, then constant

Answer 1

B

Question 2

What is the SI unit for elastic energy?

A) Newtons
B) Watts
C) Kelvins
D) Joules

Answer 2

D

Question 3

Power is a fundamental dimension.

Answer 3

False

Question 4

Power is found by dividing work by what other physical quantity?

A) distance
B) mass
C) force
D) time

Question 5

Which produces the greater change in kinetic energy (assume that all of the work goes into kinetic energy):

A) exerting a 10N force for a distance of 5m
B) exerting a force of 20N over a distance of 2m
C) exerting a 30N force for a distance of 1.5m
D) exerting a force of 40N over a distance of 1m

Question 6

A stone is dropped from a bridge and allowed to free-fall downward. As it falls a certain distance its gravitational potential energy decreases by 1000J . By how much does the stone's
Kinetic energy increase? (Neglect air resistance).

A) 100J
B) 500J
C) 1000J
D) 2200J

Question 7

What is the SI unit for work?

A) Newtons
B) Watts
C) Kelvins
D) Joules

Question 8

The law that simply states that energy is conserved is

Question 9

In the following equation, what does the x stand for? $\text { elastic energy } = \frac { 1 } { 2 } k x ^ { 2 }$

A) deflection of spring from its unstretched position
B) original length of unstretched spring
C) spring force
D) a generic unknown quantity

Question 10

A ping pong ball and a bowling ball are moving with the same momentum. Which has the greater kinetic energy?

A) The ping pong ball
B) The bowling ball

Question 11

The change in gravitational potential energy is found by multiplying an object's change in elevation by its

A) mass.
B) weight.
C) density.
D) height.

Question 12

In the following equation, what does the k stand for? $\text { elastic energy }=\frac{1}{2} k x^{2}$

A) kinetic energy
B) spring constant
C) elastic constant
D) momentum

Question 13

How much kinetic energy does a 3kg soccer ball have while moving at $20 \mathrm {~m} / \mathrm { s }$ toward your opponents' goal?

A) 60 Joules
B) -60 Joules
C) 600 Joules
D) -600 Joules

Question 14

What is the SI unit for kinetic energy?

A) Newtons
B) Watts
C) Kelvins
D) Joules

Question 15

Energy is a fundamental dimension.

Question 16

Work is found by multiplying force by what other physical quantity?

A) distance
B) mass
C) power
D) time

Question 17

Thermal energy transfer is called

A) temperature difference.
B) heat difference.
C) temperature flux.
D) heat.

Question 18

What are the SI units for heat?

A) Kelvins
B) Celsius
C) Joules
D) Watts

Question 19

How much kinetic energy does a soccer ball have while moving at $20 \mathrm {~m} / \mathrm { s }$ toward a goal?

A) 60 Joules
B) -60 Joules
C) 600 Joules
D) -600 Joules

Question 20

Which of the following requires the most work done by the brakes of a car?

Question 21

In general, efficiency is defined as

A) output divided by input.
B) input divided by output.
C) output multiplied by input.
D) output minus input.

Question 22

A team is more powerful than an individual because

A) the team can do more work than the individual in the same amount of time.
B) the team can do the same amount of work as the individual, but in less time.
C) the team can do more work than the individual in less time.
D) All of the above.

Question 23

The SI unit for power is

A) Watts
B) Joules
C) Newtons
D) Horsepower

Question 24

The time rate of doing work is called

A) energy
B) power
C) force
D) momentum

Question 25

Power can be described as

A) how hard you push.
B) how fast you push.
C) how far you push.
D) how long you push.