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

Accepted Answer

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

Accepted Answer

According to Newton's second law of motion, a constant non-zero force applied to an object will result in a change in its velocity, or acceleration. Therefore, choice A is the correct answer. Choices B, C, and D are incorrect because they imply that the velocity of the object remains unchanged, however, the application of a force will cause a change in velocity. Choice E is incorrect because acceleration is not necessarily equal to velocity, it is the rate of change of velocity.

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

Accepted Answer

The net force can be calculated using Newton's second law of motion, F = ma, where m is the mass (60 kg) and a is the acceleration (4 m/s^2). Thus, F = 60 kg * 4 m/s^2 = 240 N.

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

Accepted Answer

When air resistance equals the weight of the object, the net force acting on the object becomes zero. According to Newton's second law, acceleration is directly proportional to net force. Therefore, if net force is zero, acceleration will also be zero.

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

Accepted Answer

The answer of A force applied to an object will...

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

Accepted Answer

The efficiency of a light bulb is defined as the ratio of the light output to the electrical energy input. This is because the primary function of a light bulb is to produce light, and not heat or other forms of energy. Therefore, the best choice is (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

Accepted Answer

Pumped storage facilities store energy by pumping water to a higher elevation during periods of low demand (often at night) and release it to generate electricity during peak demand, thus increasing potential energy mainly at night.

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

Accepted Answer

Power is defined as the rate at which energy is converted or work is done over time.

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

Accepted Answer

The kinetic energy of the ball is directly proportional to its speed (KE = 1/2mv^2), and the speed of the ball is highest at position B because it has just completed its descent and is about to start ascending again. Therefore, the kinetic energy at position A will be smaller than that at position B.

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

Accepted Answer

The formula for work is Work = Force x Distance. 
In this case, the force needed to lift the object is its weight, which is 70 lbs. 
The distance it needs to be lifted is 14 feet.

Therefore, the work required is: 
Work = 70 lbs x 14 feet 
Work = 980 ft-lbs

Thus, the minimum work the motor must do is 980 ft-lbs, which is option D.

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%

Accepted Answer

The answer of If the energy conversion efficiencies in a...

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

Accepted Answer

According to Newton's Third Law of Motion, for every action, there is an equal and opposite reaction. In this case, the action force is the push that you give to the bike, and the reaction force is the force of the bike upon you.

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

Accepted Answer

According to the laws of thermodynamics, it is impossible for any system to convert all of the input energy into useful work. In a fossil fueled electrical generating plant, only about one-third of the chemical energy will be converted into electricity, while the remaining two-thirds will be lost as waste heat. Therefore, for every 10,000 Btu of chemical energy input, about 6,000 Btu of waste heat will be dumped into the environment.

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¢

Accepted Answer

To calculate the cost of running a set of eight 100 watt light bulbs for 6 hours, first we need to calculate the total energy used:

Total Energy = Power x Time
Total Energy = 8 bulbs x 100 watts/bulb x 6 hours
Total Energy = 48,000 watt-hours

To convert watt-hours to kilowatt-hours (kWh), we divide by 1000:

Total Energy in kWh = 48,000 watt-hours / 1000
Total Energy in kWh = 48 kWh

Now we can calculate the cost of electricity:

Cost = Energy x Rate
Cost = 48 kWh x $0.09/kWh
Cost = $4.32

To find the cost for 6 hours, we need to divide by the number of hours:

Cost for 6 hours = $4.32 / 6
Cost for 6 hours = $0.72

Therefore, 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 72¢. So, the best choice is C.

Question 15

Which of the following is a unit of energy:
A) watt
B) ft-lb/sec
C) newton/sec.
D) horsepower
E) joule

Accepted Answer

Joule is the unit of energy, defined as the amount of work done when a force of one newton is applied over a distance of one meter. Watt is the unit of power, ft-lb/sec is a unit of torque, newton/sec is a unit of force, and horsepower is a unit of power.

Question 16

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

A)A
B) B
C) C

Accepted Answer

The kinetic energy of an object in motion is given by the equation KE=1/2mv^2, where m is the mass of the object and v is its velocity. At point B, the nosecracker is at its maximum velocity, which means it has the greatest kinetic energy. At points A and C, the velocity of the nosecracker is zero, so there is no kinetic energy.

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

Accepted Answer

According to Newton's first law of motion, a body at rest or in motion with a constant velocity will remain in that state unless acted upon by a net external force. Therefore, if a body is moving at a constant velocity in outer space, it must be experiencing no net external force. Hence the net force required to move a body at a constant velocity in outer space is zero.

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

Accepted Answer

We know that force=mass x acceleration, so the acceleration of the 10 kg block is 30/10=3 m/s^2. To achieve the same acceleration in the 5 kg block, we need to use the same formula and solve for force: force=mass x acceleration, force=5 x 3 = 15 N. Therefore, the answer is C, 15 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

Accepted Answer

The time taken for sound to travel from one side to another and back is 4 seconds. Therefore, the time taken for sound to travel one way is 2 seconds. 
Using the formula: distance = velocity x time, we have 
distance = 300 x 2 = 600 meters. 
Therefore, the other side of the canyon is 600 meters away.

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

Accepted Answer

The acceleration can be calculated using Newton's second law: a = F/m = 30 N / 3 kg = 10 m/s². Using the kinematic equation v² = u² + 2as, where u = 0, a = 10 m/s², and s = 5 m, we find v² = 0 + 2(10)(5) = 100, so v = √100 = 10 m/s.

Quiz 2: Energy Mechanics

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 _____.

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

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 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 force applied to an object will always cause the object to

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

Pumped storage facilities ________.

Power is defined as ________.

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

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?

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:

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

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:

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:

Which of the following is a unit of energy:

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

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

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 ________.

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) .

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.