Deck 2: Energy Mechanics

Question 1

If the height of water behind a dam is increased by a factor of two, then the maximum kinetic energy of the water at the bottom of the dam will increase by a factor of _____.

A) one
B) two
C) four
D) zero

Answer 1

B

Question 2

If a constant non-zero force is applied to an object, its velocity will certainly ________.

A) change
B) stop
C) be zero
D) be constant
E) equal acceleration

Answer 2

A

Question 3

If a 60 kg person is observed to accelerate at a rate of 4 m/sec/sec, the net force responsible for this is:

A) 600 N
B) 240 N
C) 30 N
D) the force of gravity
E) 480 N

Answer 3

B

Question 4

A 100 lb sack of potatoes falls from an airplane. As the velocity of fall increases, the air resistance also increases. When air resistance equals 100 lb, the acceleration of the sack will be ____ m/sec/sec.

A) 0
B) 16
C) 32
D) 9.8
E) 24

Question 5

A force applied to an object will always cause the object to

A) speed up
B) accelerate
C) change its momentum
D) all of the above
E) none of the above

Question 6

The "efficiency" of a light bulb is the ratio of the:

A) heat plus electricity produced to the electrical input
B) voltage output of the bulb to the power input
C) energy into the bulb to the energy out of the bulb
D) light output to the electrical energy input

Question 7

Pumped storage facilities ________.

A) increase the overall efficiency of a power plant
B) make use of the output of electricity from photovoltaic cells
C) are used to produce electricity mainly at night
D) have an increase in their potential energy mainly at night
E) cannot be used with a nuclear plant

Question 8

Power is defined as ________.

A) the energy used times the time
B) the work done times the distance of motion
C) the energy used divided by the work
D) the rate of converting energy
E) the ability to do work

Question 9

A ball rolls back and forth on the track shown. The kinetic energy at position A will be _________ than that at position B.

A) greater
B) smaller
C) the same as

Question 10

What is the minimum work that a motor must do to lift a 70 lb object from the floor to a height of 14 feet?

A) 5
B) 70
C) 700
D) 980
E) 2010 ft-lbs

Question 11

If the energy conversion efficiencies in a 3 step process are 30% for the first step, 40% for the second, and 20% for the third, the overall efficiency (step one to end) is about:

A) 2%
B) 10%
C) 20%
D) 50%
E) 90%

Question 12

If the push that you give to a bike is the action force, then the reaction force is ________.

A) the force of the bike upon you
B) the weight of the bike
C) the friction force on the tires
D) the acceleration of the bike
E) air resistance on the bike

Question 13

For a fossil fueled electrical generating plant, 10,000 Btu of chemical energy into the plant will result in about how many Btu's of waste heat dumped into the environment:

A) 0
B) 1000
C) 4000
D) 6000
E) 10,000 Btu's

Question 14

The cost of running a set of eight 100 watt light bulbs for 6 hours, with the cost of electricity at 9¢ per kWh, is approximately:

A) 5¢
B) 24¢
C) 43¢
D) 54¢
E) 72¢

Question 15

Which of the following is a unit of energy:

A) watt
B) ft-lb/sec
C) newton/sec.
D) horsepower
E) joule

Question 16

Our nosecracker moved back and forth as shown. The kinetic energy will be greatest at point:

A )A
B) B
C) C

Question 17

The net force required to move a body at a constant velocity in outer space is ________.

A) zero
B) its weight
C) the force of gravity
D) its mass times its velocity
E) the force of friction

Question 18

A net force of 30 newtons is applied to a block of mass 10 kg. The force that must be applied to a block of mass 5 kg to give it equal acceleration is ________.

A) 5
B) 10
C) 15
D) 20
E) 30 N

Question 19

If you shout across a canyon and the echo returns in four seconds, how far away is the other side? (Velocity of sound in air is 300 m/s).

A) 150
B) 300
C) 600
D) 1200
E) 2400 meters

Question 20

If a net force of 30 newtons is applied to a cart of mass 3 kg at rest, the velocity of the cart at the end of 5 meters will be ____ m/s.

A) 5
B) 10
C) 12
D) 25
E) 30

Question 21

How much work is required to increase the velocity of a 4 kg car from rest to 5 m/sec?

A) 10
B) 20
C) 50
D) 100
E) 200 Joules

Question 22

A sheet of paper can be withdrawn from under a bottle of milk without toppling the bottle if the paper is jerked out quickly. This is an example of ________.

A) inertia
B) action-reaction
C) potential energy
D) friction forces

Question 23

When a car is braked to a stop, its kinetic energy is transformed into

A) stopping energy
B) potential energy
C) heat energy
D) energy of motion

Question 24

Which of the following is a unit of power?

A) Btu
B) kilowatt
C) kilowatt-hour
D) joule
E) horsepower per hour

Question 25

The reason that you would use a ramp to carry a weight to the top of a platform, rather than lifting it up a ladder, is because the

A) force exerted would be less
B) work done would be less
C) power expended would be less
D) gain in potential energy would be more

Question 26

If the same force is applied to a 2 kg object as to a 1 kg one, _______.

A) the velocity of the 2 kg object will be greater after 2 sec.
B) the distance traveled in the same time will be more for the 1 kg object
C) the acceleration of the larger object will be more
D) the acceleration of the 1 kg object will be 4 times more