Chapter 4

Question 1

Which of the following is an example in which you are traveling at constant speed, but not at constant velocity?
A) rolling freely down a hill in a cart, traveling in a straight line
B) driving backward at exactly 50 km/hr
C) driving around in a circle at exactly 100 km/hr
D) jumping up and down exactly 60 times per minute
E) none of the above

Answer 1

C) driving around in a circle at exactly 100 km/hr

Question 2

Which of the following correctly states the value and units of the acceleration of gravity on Earth?
A) 9.8 m/s^2
B) 9.8 m/s
C) 9.8 km/s^2
D) 9.8 m^2/s

Answer 2

A) 9.8 m/s^2

Question 3

Momentum is defined as
A) mass times speed.
B) mass times velocity
C) force times velocity
D) mass times acceleration

Answer 3

B) mass times velocity

Question 4

If an object’s velocity is doubled, its momentum is
A) halved
B) unchanged
C) doubled
D) quadrupled

Answer 4

C) doubled

Question 5

As long as an object is not gaining or losing mass, a net force on the object will cause a change in
A) acceleration
B) direction
C) weight
D) speed
E) velocity

Answer 5

E) velocity

Question 6

If your mass is 60 kilograms on Earth, what would your mass be on the Moon?
A) 10 pounds
B) 10 kilograms
C) 360 kilograms
D) 60 kilograms

Answer 6

D) 60 kilograms

Question 7

In which of the following cases would you feel weightless?
A) while walking on the Moon
B) while falling from an airplane with your parachute open
C) while traveling through space in an accelerating rocket
D) while falling from a roof
E) none of the above

Answer 7

D) while falling from a roof

Question 8

Astronauts are weightless inside the International Space Station because
A) the station and the astronauts are constantly falling toward Earth
B) the station has rockets that fire to counteract Earth’s gravity
C) there is no gravity in space
D) the station is too far from Earth for gravity to be noticeable

Answer 8

A) the station and the astronauts are constantly falling toward Earth

Question 9

You are standing on a scale in an elevator and notice that your weight is lower than your normal weight. What do you conclude is occurring?
A) The elevator is accelerating upward
B) The elevator is moving at a constant velocity upward
C) The elevator is accelerating downward
D) The elevator is moving at a constant velocity downward
E) Your diet is working.

Answer 9

C) The elevator is accelerating downward

Question 10

Two bowling balls with different masses are dropped from the same height. How do their accelerations compare?
A) The heavier bowling ball accelerates faster
B) They both fall with the same acceleration
C) The lighter bowling ball accelerates faster

Answer 10

B) They both fall with the same acceleration

Question 11

How could you test the hypothesis that the acceleration of gravity does not depend on mass? (Ignore effects of air resistance.)
A) Drop two objects with the same mass from the same height
B) Drop two objects with the same mass from different heights
C) Drop two objects with different masses from the same height
D) Drop two objects with different masses from different heights

Answer 11

C) Drop two objects with different masses from the same height

Question 12

Suppose you drop a feather and a hammer on the Moon from the same height at the sametime. What will happen?
A) The feather will hit the ground first
B) They will hit the ground at the same time
C) The hammer will hit the ground first
D) They will float at the height you release them

Answer 12

B) They will hit the ground at the same time

Question 13

Suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen?
A) The 10-pound weight will hit the ground before the 5-pound weight
B) Both will hit the ground at the same time
C) Both weights will float freely, since everything is weightless on the Moon

Answer 13

B) Both will hit the ground at the same time

Question 14

Suppose an object is moving in a straight line at 50 miles/hr. According to Newton’s first law of motion, the object will
A) continue to move in a straight line at 50 miles/hr forever, no matter what happens
B) continue to move in a straight line at 50 miles/hr until it is acted upon by a net force
C) eventually slow down and come to a stop
D) continually slow down, but never quite come to a complete stop

Answer 14

B) continue to move in a straight line at 50 miles/hr until it is acted upon by a net force

Question 15

You observe an object to be moving in a straight line at a constant speed. What can you conclude? (Assume the object does not have any engines or other power source.)
A) The net force acting on the object is zero
B) No forces of any kind are acting on the object
C) The only force acting on the object is gravity
D) The only force acting on the object is air resistance
E) Some unseen force must be keeping the object in motion

Answer 15

A) The net force acting on the object is zero

Question 16

An astronaut in space swings a ball attached to a string in a circular motion. If the string suddenly breaks, how will the ball move?
A) It will move in a straight line in whichever direction it was moving when the string broke
B) It will continue to move in the same circular path it had been following before the stringbroke
C) It will instantly come to a stop
D) It will move toward the astronaut
E) It will move in a large elliptical path around the astronaut

Answer 16

A) It will move in a straight line in whichever direction it was moving when the string broke

Question 17

Consider Newton’s second law states, often written as force = mass × acceleration. Based on this law, what property can you determine if you observe the acceleration of an object with a known mass?
A) the net force acting on the object
B) the strength of gravity acting on the object
C) the current velocity of the object
D) the current location of the object

Answer 17

A) the net force acting on the object

Question 18

The idea that we live in a universe (literally, “one story”), in which the same law of gravity applies both on Earth and in space, was established through the work of
A) Newton
B) Copernicus
C) Kepler
D) Galileo

Answer 18

A) Newton

Question 19

Which person realized the laws of gravity applied to objects both on Earth and in space?
A) Newton
B) Copernicus
C) Kepler

Answer 19

A) Newton

Question 20

The Earth exerts a gravitational force on a person standing on the surface. The person also exerts a gravitational force on the Earth. Based on Newton’s third law of motion, how do these two forces compare?
A) The forces exerted by the Earth and the person are the same
B) The Earth exerts a much stronger force than the person
C) The person exerts a much stronger force than the Earth
D) The Earth exerts a slightly stronger force than the person

Answer 20

A) The forces exerted by the Earth and the person are the same

Question 21

How does a rocket take off?
A) Its rocket engines push against the launch pad, propelling the rocket upward
B) It converts mass-energy to kinetic energy
C) It achieves lift from its wings in the same way that airplanes do
D) Hot gas shoots out from the back of the rocket and, by conservation of momentum, the rocket moves in the opposite direction
E) The hot rocket exhaust expands the air beneath the rocket, propelling it forward

Answer 21

D) Hot gas shoots out from the back of the rocket and, by conservation of momentum, the rocket moves in the opposite direction

Question 22

How does a rocket launch upward? Choose the statement that correctly answers the question
A) By expelling gas downward, the rocket is propelled upward
B) Expelling gas downward, which by pushing against the ground, propels the rocket upward

Answer 22

A) By expelling gas downward, the rocket is propelled upward

Question 23

Angular momentum depends upon
A) mass and velocity
B) mass, velocity, and radius
C) force and radius

Answer 23

B) mass, velocity, and radius

Question 24

Which law explains why a skater can spin faster by pulling his arms closer to his body, or spins lower by spreading his arms out?
A) the law of gravity
B) Newton’s third law of motion
C) the law of conservation of momentum
D) the law of conservation of angular momentum

Answer 24

D) the law of conservation of angular momentum

Question 25

Suppose the Sun were to suddenly shrink in size but its mass remained the same. According to the law of conservation of angular momentum, what would happen?
A) The Sun’s angular size in our sky would increase
B) The Sun’s rate of rotation would slow
C) The Sun’s rate of rotation would remain the same
D) The Sun rate of rotation would increase

Answer 25

D) The Sun rate of rotation would increase

Question 26

Which of the following is not a conserved quantity?
A) energy
B) momentum
C) angular momentum
D) radiation

Answer 26

D) radiation

Question 27

Which of the following is the standard international unit for measuring energy?
A) Kelvin
B) joule
C) watt
D) newton
E) meter

Answer 27

B) joule

Question 28

Radiative energy is
A) heat energy
B) energy from nuclear power plants
C) energy carried by light
D) energy used to power home radiators
E) energy of motion

Answer 28

C) energy carried by light

Question 29

Gasoline can be used to power cars because it has
A) gravitational potential energy
B) chemical potential energy
C) electrical potential energy
D) kinetic energy
E) radiative energy

Answer 29

B) chemical potential energy

Question 30

What does temperature measure?
A) the average mass of particles in a substance
B) the average size of particles in a substance
C) the average kinetic energy of particles in a substance
D) the total number of particles in a substance
E) the total potential energy of particles in a substance

Answer 30

C) the average kinetic energy of particles in a substance

Question 31

On a hot day, molecules of air ________ than on a cold day.
A) move faster on average
B) move slower on average
C) are more massive
D) are less massive
E) contain more atoms

Answer 31

A) move faster on average

Question 32

The amount of gravitational potential energy released as an object falls depends on
A) its mass, the distance it falls, and the acceleration of gravity
B) its mass and its speed at the time it begins falling
C) its mass and its speed when it hits the ground

Answer 32

A) its mass, the distance it falls, and the acceleration of gravity

Question 33

Which of the following statements correctly describes the law of conservation of energy?
A) An object always has the same amount of energy
B) Energy can change between many different forms, such as potential, kinetic, and thermal, but it is ultimately destroyed
C) Energy can change between many different forms, such as potential, kinetic, and thermal, but the total quantity of energy in the universe never change

Answer 33

C) Energy can change between many different forms, such as potential, kinetic, and thermal, but the total quantity of energy in the universe never change

Question 34

Where does your body get the energy it uses to make your heart beat?
A) It comes from the radiative energy of the sunlight that hits your skin.
B) It comes from the chemical potential energy of the food you eat.
C) It comes from the thermal energy of the water you drink

Answer 34

B) It comes from the chemical potential energy of the food you eat

Question 35

When a rock is held above the ground, we say it has some gravitational potential energy. When we let it go, it falls and we say the gravitational potential energy is converted to kinetic energy. Finally, the rock hits the ground (and stays there). What has happened to the energy?
A) The rock keeps the energy inside it in the form of mass-energy
B) The energy goes into the ground and, as a result, the orbit of Earth about the Sun is slightly changed
C) It is transformed back into gravitational potential energy
D) The energy goes to producing sound and to heating the ground, rock, and surrounding air

Answer 35

D) The energy goes to producing sound and to heating the ground, rock, and surrounding air

Question 36

According to the universal law of gravitation, the force due to gravity is
A) directly proportional to the square of the distance between objects
B) inversely proportional to the square of the distance between objects
C) directly proportional to the distance between objects
D) inversely proportional to the distance between objects
E) not dependent on the distance between objects

Answer 36

B) inversely proportional to the square of the distance between objects

Question 37

According to the universal law of gravitation, if the masses of both attracting objects double,then the gravitational force between them will
A) not change at all
B) increase by a factor of 2
C) decrease by a factor of 2
D) increase by a factor of 4
E) decrease by a factor of 4

Answer 37

D) increase by a factor of 4

Question 38

Gravity follows an inverse square law. This means that if the distance between two masses is decreased by a factor of 4, the gravitational force between those two masses
A) increases by a factor of 16
B) increases by a factor of 4
C) increases by a factor of 2
D) decreases by a factor of 4

Answer 38

A) increases by a factor of 16

Question 39

The gravitational force between two objects can be described using the equation Fg = G M1M2 / d^2. In this equation, what does d represent?
A) the universal gravitational constant
B) the density of the smaller object
C) the distance between the two objects
D) the diameter of the larger object

Answer 39

C) the distance between the two objects

Question 40

The gravitational force between two objects can be described using the equation Fg = G M1M2 / d^2. According to this equation, if the distance between two objects increases, what happens to the gravitational force between them?
A) The force increases.
B) The force decreases.
C) The force drops instantly to zero.
D) The gravitational force is not affected by distance

Answer 40

B) The force decreases.

Question 41

Which of the following describes a velocity (as opposed to a speed)?
A) 20 kilometers per hour, headed north
B) 300,000 kilometers per second
C) 9.8 meters per second squared (m/s2)

Answer 41

A) 20 kilometers per hour, headed north

Question 42

The acceleration of gravity on Earth is approximately 10 m/s^2 (more precisely, 9.8 m/s^2). If you drop a rock from a tall building, about how fast will it be falling after 3 seconds?
A) 30 m/s
B) 10 m/s
C) 30 m/s2
D) 10 m/s2
E) 20 m/s

Answer 42

A) 30 m/s

Question 43

Which of the following examples describes a situation where a car is experiencing a net force?
A) The car is holding constant speed around a curve.
B) The car is holding constant speed down a straight hill because the driver is applying the brakes.
C) The car is moving at constant speed in a straight line.
D) The car is stopped on a hill

Answer 43

A) The car is holding constant speed around a curve.

Question 44

Suppose you lived on the Moon. Which of the following would be true?
A) Your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.
B) Both your weight and your mass would be less than they are on Earth.
C) Your mass would be less than your mass on Earth, but your weight would be the same as it is on Earth.
D) Both your weight and your mass would be the same as they are on Earth.

Answer 44

A) Your weight would be less than your weight on Earth, but your mass would be the same as itis on Earth.

Question 45

Which of the following statements is not one of Newton’s Laws of Motion?
A) What goes up must come down.
B) The rate of change of momentum of an object is equal to the net force applied to the object.
C) In the absence of a net force acting on it, an object moves with constant velocity.
D) For any force, there always is an equal and opposite reaction force

Answer 45

A) What goes up must come down.

Question 46

When a spinning ice skater pulls in his arms, he spins faster because
A) his angular momentum must be conserved, so reducing his radius must increase his speed of rotation.
B) there is less friction with the air.
C) there is less friction with the ice.
D) there exists an unbalanced reaction force

Answer 46

A) his angular momentum must be conserved, so reducing his radius must increase his speed of rotation.

Question 47

What does temperature measure?
A) the average kinetic energy of particles in a substance
B) the average mass of particles in a substance
C) the total potential energy of particles in a substance
D) the total amount of heat in a substance

Answer 47

A) the average kinetic energy of particles in a substance