Question 1

The vertical speed of a projectile
A) is zero.
B) stays constant.
C) continuously increases.
D) continuously decreases.
E) sometimes decreases and sometimes increases.

Accepted Answer

The vertical speed of a projectile decreases as it rises due to gravity, reaches zero at its peak, and then increases as it falls back down, thus it sometimes decreases and sometimes increases.

Question 2

A body is oscillating up and down at the end of a spring. Let's consider when the body is at the top of its up-and-down motion. The velocity
A) is zero.
B) has its largest magnitude.
C) points up.
D) points down.

Accepted Answer

When a body is at the top of its up-and-down motion, its velocity is zero. This is because it has reached the highest point in its motion and is about to reverse direction and start moving downwards. Thus, option A is the correct choice. Option B is incorrect because the velocity at the highest point is zero, so it cannot have its largest magnitude. Options C and D are also incorrect because the direction of the velocity at the highest point depends on the direction of the motion leading up to that point, and could be either up or down.

Question 3

As a body falls through air starting from rest, its acceleration
A) is zero.
B) stays constant.
C) continuously decreases.
D) continuously increases.
E) gets smaller and smaller, eventually approaching zero.

Accepted Answer

As a body falls through air starting from rest, its acceleration initially is due to gravity. However, as its speed increases, air resistance also increases. This air resistance opposes the motion, reducing the net acceleration. Eventually, the force due to air resistance balances the gravitational pull, and the body moves with constant velocity (terminal velocity), making the acceleration approach zero.

Question 4

For this situation, I push on a heavy chair. Suppose I push lightly on the chair, and the chair doesn't move at all. Then the strength of the force the chair exerts on me is
A) less than the force I exert on the chair.
B) equal to the force I exert on the chair.
C) greater than the force I exert on the chair.
D) zero.

Accepted Answer

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. When I push on the chair, the chair exerts an equal and opposite force on me. Therefore, the strength of the force the chair exerts on me is equal to the force I exert on the chair. If the chair didn't move at all, it means that the forces are balanced, so the answer is B.

Question 5

The horizontal speed of a projectile
A) is zero.
B) stays constant.
C) continuously increases.
D) continuously decreases.
E) sometimes decreases and sometimes increases.

Accepted Answer

The horizontal speed of a projectile is constant and does not change during the motion, assuming there is no air resistance. This is because there is no force acting on the projectile in the horizontal direction, so it will continue to move at a constant speed.

Question 6

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. After moving downwards at constant speed, the elevator is slowing down at 2 m/s ² as it is coming to rest. A) 150 lb B) 160 lb C) 170 lb D) none of the above

Accepted Answer

When the elevator is slowing down (decelerating) while moving downwards, the apparent weight of the person increases. This is because the deceleration of the elevator adds to the gravitational force, making the person feel heavier. Therefore, the scale would read more than the person's actual weight of 160 lb, making 170 lb the correct choice.

Question 7

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale.  Determine the scale reading for the given scenarios. The elevator cable breaks.
A) 150 lb
B) 160 lb
C) 170 lb
D) none of the above

Accepted Answer

The scale reading would be the same as the person's weight, which is 160 lb, regardless of whether the elevator is moving or not. When the cable breaks, the elevator and the person inside would be in free fall, so there would be no net force acting on them, and they would experience weightlessness. Therefore, the scale reading would be zero.

Question 8

For this situation, I push on a heavy chair. Suppose I push very hard on the chair, and this time the chair moves and I slip backward as well. Then the strength of the force the chair exerts on me is
A) less than the force I exert on the chair.
B) equal to the force I exert on the chair.
C) greater than the force I exert on the chair.
D) zero.

Accepted Answer

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. In this case, the force I exert on the chair is equal in magnitude and opposite in direction to the force the chair exerts on me. Therefore, the strength of the force the chair exerts on me is equal to the force I exert on the chair.

Question 9

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale.  Determine the scale reading for the given scenarios. The elevator accelerates downwards and is now moving at a constant speed.
A) 150 lb
B) 160 lb
C) 170 lb
D) none of the above

Accepted Answer

When the elevator moves at a constant speed, there is no net acceleration acting on the person. Therefore, the scale will read the actual weight of the person, which is 160 lb.

Question 10

The horizontal acceleration of a projectile
A) is zero.
B) stays constant.
C) continuously increases.
D) continuously decreases.
E) sometimes decreases and sometimes increases.

Accepted Answer

The horizontal acceleration of a projectile is zero as it is not under any horizontal force or acceleration. Instead, it moves with a constant velocity in the horizontal direction.

Question 11

The vertical acceleration of a projectile
A) equals g pointing downwards.
B) equals g pointing upwards.
C) equals g pointing sometimes upwards and other times downwards.
D) is zero.
E) continuously increases.

Accepted Answer

The vertical acceleration of a projectile is the acceleration due to gravity (g), which always points downwards. Therefore, option A is correct.

Question 12

You throw a ball straight up, it peaks out, and then comes back down to you. During this motion, the velocity and acceleration
A) always point in the same direction.
B) always point opposite to each other.
C) sometimes point in the same direction, and other times point opposite to each other.
D) depend on the way the ball is thrown.
E) depend on the mass of the ball.

Accepted Answer

At the highest point, the velocity is zero and acceleration is still acting downwards due to gravity. As the ball starts to come down, the velocity and acceleration point in opposite directions until it hits the ground. Therefore, the velocity and acceleration sometimes point in the same direction and other times point opposite to each other.

Question 13

For this situation, I push on a heavy chair. Suppose I push moderately on the chair, and this time the chair does move. Then the strength of the force the chair exerts on me is
A) less than the force I exert on the chair.
B) equal to the force I exert on the chair.
C) greater than the force I exert on the chair.
D) zero.

Accepted Answer

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. In this situation, I am exerting a force on the chair to move it, and hence the chair is exerting an equal and opposite force on me. Therefore, the strength of the force the chair exerts on me is equal to the force I exert on the chair.

Question 14

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. The elevator is accelerating downwards at 2 ft/s ². A) 150 lb B) 160 lb C) 170 lb D) none of the above

Accepted Answer

When the elevator accelerates downwards, the apparent weight of the person decreases. The apparent weight can be calculated using the formula $w = m(g - a)$, where $m$ is the mass in slugs, $g$ is the acceleration due to gravity (32 ft/s$^2$), and $a$ is the acceleration of the elevator (2 ft/s$^2$ downwards). For a 160 lb person (mass = 5 slugs), the apparent weight in the elevator is $w = 5(32 - 2) = 5(30) = 150$ lb.

Question 15

Two cars crash head on. At any given time during the crash, the magnitudes of the collision forces exerted on each car are exactly equal. This is an example of Newton's
A) first law.
B) second law.
C) third law.
D) no law.

Accepted Answer

This is an example of Newton's third law, which states that for every action there is an equal and opposite reaction. In this case, the action is the force exerted by one car on the other during the collision, and the reaction is the equal and opposite force exerted by the second car on the first.

Question 16

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. After moving upwards at constant speed, the elevator is slowing down at 2 m/s ² as it is coming to rest. A) 150 lb B) 160 lb C) 170 lb D) none of the above

Accepted Answer

When the elevator is slowing down while moving upwards, the apparent weight decreases. The deceleration of 2 m/s² reduces the normal force, making the scale read less than the actual weight.

Question 17

Planetary orbits are
A) parabolas.
B) ellipses.
C) circles.
D) none of the above.

Accepted Answer

Planetary orbits are actually ellipses, with the Sun located at one of the two foci. This phenomenon is known as Kepler's First Law of Planetary Motion.

Question 18

As a body falls through air starting from rest, its velocity
A) stays constant.
B) continuously decreases.
C) continuously increases.
D) gets larger and larger, eventually reaching a constant value.
E) gets smaller and smaller, eventually approaching zero.

Accepted Answer

As a body falls through air from rest, its velocity initially increases due to the acceleration due to gravity. However, as its velocity increases, the air resistance acting against it also increases. Eventually, the force due to air resistance balances the gravitational force, and the body reaches a terminal velocity, where its velocity becomes constant.

Question 19

At the highest point on the path of a projectile, its vertical acceleration
A) equals g pointing downwards.
B) equals g pointing upwards.
C) is zero.
D) is undetermined.
E) does not exist.

Accepted Answer

At the highest point of its trajectory, a projectile's vertical velocity is zero, but its acceleration due to gravity (g) still acts downwards.

Question 20

Where is the Sun located relative to a planet's orbit about it?
A) at the center of the orbit, which is a circle
B) at the center of the orbit, which is an ellipse
C) at one focus of the ellipse which forms the orbit
D) none of the above

Accepted Answer

According to Kepler's laws of planetary motion, the Sun is located at one focus of the ellipse which forms the planet's orbit, with the planet itself located at the other focus.

Quiz 2: Newton S Laws

The vertical speed of a projectile

A body is oscillating up and down at the end of a spring. Let's consider when the body is at the top of its up-and-down motion. The velocity

As a body falls through air starting from rest, its acceleration

For this situation, I push on a heavy chair. Suppose I push lightly on the chair, and the chair doesn't move at all. Then the strength of the force the chair exerts on me is

The horizontal speed of a projectile

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. After moving downwards at constant speed, the elevator is slowing down at 2 m/s 2 as it is coming to rest.

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. The elevator cable breaks.

For this situation, I push on a heavy chair. Suppose I push very hard on the chair, and this time the chair moves and I slip backward as well. Then the strength of the force the chair exerts on me is

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. The elevator accelerates downwards and is now moving at a constant speed.

The horizontal acceleration of a projectile

The vertical acceleration of a projectile

You throw a ball straight up, it peaks out, and then comes back down to you. During this motion, the velocity and acceleration

For this situation, I push on a heavy chair. Suppose I push moderately on the chair, and this time the chair does move. Then the strength of the force the chair exerts on me is

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. The elevator is accelerating downwards at 2 ft/s 2.

Two cars crash head on. At any given time during the crash, the magnitudes of the collision forces exerted on each car are exactly equal. This is an example of Newton's

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. After moving upwards at constant speed, the elevator is slowing down at 2 m/s 2 as it is coming to rest.

Planetary orbits are

As a body falls through air starting from rest, its velocity

At the highest point on the path of a projectile, its vertical acceleration

Where is the Sun located relative to a planet's orbit about it?

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. After moving downwards at constant speed, the elevator is slowing down at 2 m/s ² as it is coming to rest.

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. The elevator is accelerating downwards at 2 ft/s ².

A 160 lb person has a mass of 160/32 = 5 slugs. A 160-lb person steps into an elevator and stands on a bathroom scale. Determine the scale reading for the given scenarios. After moving upwards at constant speed, the elevator is slowing down at 2 m/s ² as it is coming to rest.