Question 1

Twelve seconds after starting from rest, an object falling freely will have a speed of
A) 10 m/s.
B) 100 m/s.
C) 50 m/s.
D) more than 100 m/s.

Accepted Answer

An object in free fall accelerates at approximately 9.8 m/s². After 12 seconds, its speed is 9.8 m/s² * 12 s = 117.6 m/s, which is more than 100 m/s.

Question 2

Disregarding air resistance, objects fall with constant
A) speed.
B) acceleration.
C) velocity.
D) distances each successive second.

Accepted Answer

Disregarding air resistance, objects in free fall near the Earth's surface experience constant acceleration due to gravity, approximately 9.8 m/s^2, regardless of their mass.

Question 3

A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before
Striking the water
A) is greater for the fired bullet.
B) is the same for each bullet.
C) is greater for the dropped bullet.
D) depends on how high they started.
E) none of these

Accepted Answer

Both bullets experience the same acceleration due to gravity just before striking the water, as acceleration due to gravity is constant and does not depend on the initial velocity of the objects.

Question 4

A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always
A) directed downward.
B) opposite its velocity.
C) directed upward.
D) in the direction of motion.

Accepted Answer

The acceleration of the ball is always directed downward due to gravity, regardless of the direction of its velocity.

Question 5

Galileo's use of inclined planes allowed him to effectively
A) eliminate the acceleration of free fall.
B) increase the acceleration beyond that of free fall.
C) slow down the acceleration of free fall.
D) eliminate friction.

Accepted Answer

Galileo's use of inclined planes slowed down the acceleration due to gravity, making it easier to measure and observe the motion of objects. This method did not eliminate or increase the acceleration of free fall, nor did it eliminate friction, but it allowed for a more manageable study of the principles of motion.

Question 6

While an object near the earth's surface is in free fall , its
A) velocity increases.
B) acceleration increases.
C) mass increases.
D) mass decreases.

Accepted Answer

During free fall near the Earth's surface, an object's velocity increases due to the constant acceleration caused by gravity, which is approximately 9.8 m/s^2. The acceleration due to gravity remains constant, and the mass of the object does not change.

Question 7

An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as it is on Earth. In the first 5 seconds it falls a distance of
A) 250 m.
B) 150 m.
C) 100 m.
D) 500 m.
E) none of these

Accepted Answer

The distance an object falls freely from rest can be calculated using the formula $d = \frac{1}{2}gt^2$, where $g$ is the acceleration due to gravity and $t$ is the time in seconds. On Earth, $g = 9.8 \, \text{m/s}^2$, but on this planet, $g$ is twice that, so $g = 19.6 \, \text{m/s}^2$. Plugging in the values, $d = \frac{1}{2} \times 19.6 \times 5^2 = 245 \, \text{m}$, which rounds to 250 m, making option A correct.

Question 8

If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be
A) 3600 m/s.
B) 50 m/s.
C) 3000 m/s.
D) 500 m/s.

Accepted Answer

The speed can be calculated using the formula: speed = acceleration × time. Here, acceleration = 50 m/s² and time = 60 seconds (1 minute), so speed = 50 × 60 = 3000 m/s.

Question 9

If a car accelerates from rest at 2 meters per second per second, its speed 3 seconds later will be about
A) 3 m/s.
B) 4 m/s.
C) 2 m/s.
D) 6 m/s.

Accepted Answer

The speed of the car can be calculated using the formula: final speed = initial speed + (acceleration × time). Since the car starts from rest, the initial speed is 0. Therefore, final speed = 0 + (2 m/s² × 3 s) = 6 m/s.

Question 10

A pot falls from a ledge and hits the ground 45 m below. The speed with which it hits the ground is
A) about 120 m/s.
B) about 30 m/s.
C) about 60 m/s.
D) more than 120 m/s.

Accepted Answer

The speed with which the pot hits the ground can be calculated using the formula $v = \sqrt{2gh}$, where $g = 9.8 \, \text{m/s}^2$ is the acceleration due to gravity and $h = 45 \, \text{m}$ is the height. Plugging in the values, we get $v = \sqrt{2 \times 9.8 \times 45} \approx 29.9 \, \text{m/s}$, which is about 30 m/s.

Question 11

If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about
A) 2 seconds.
B) 10 seconds.
C) 20 seconds.
D) 1 second.
E) not enough information to estimate

Accepted Answer

The time to reach the highest point is given by t = v/g, where v is the initial velocity (10 m/s) and g is the acceleration due to gravity (approximately 9.8 m/s²). So, t = 10/9.8 ≈ 1 second. The total time for the round trip is twice this, so approximately 2 seconds.

Question 12

Disregarding air drag, how fast must you toss a ball straight up in order for it to take 2 seconds to return to the level from which you tossed it?
A) 10 m/s
B) 20 m/s
C) 15 m/s
D) 5 m/s
E) 7.5 m/s

Accepted Answer

The ball takes 1 second to reach the peak of its trajectory, where its velocity is 0 m/s. Using the formula $v = u + at$, where $v$ is the final velocity (0 m/s at the peak), $u$ is the initial velocity, $a$ is the acceleration due to gravity (-9.8 m/s$^2$, negative because it's acting in the opposite direction of the toss), and $t$ is the time (1 second to reach the peak), we can solve for $u$: $0 = u - 9.8 \times 1$, giving $u = 9.8 m/s$. However, since the question asks for the speed to return to the level from which it was tossed, we consider the speed at the moment of the toss, which needs to be enough to reach the peak and return, effectively doubling the time in the air to 2 seconds. The correct calculation should directly use the total time of 2 seconds, where the speed needed is $9.8 m/s^2 \times 1 s = 9.8 m/s$, but since we're looking for an answer in the options provided, 10 m/s is the closest correct answer, allowing for the ball to reach the peak and return in 2 seconds.

Question 13

A car accelerates at 2 meters per second per second. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 30 m/s?
A) 2 seconds
B) 15 seconds
C) 60 seconds
D) 30 seconds
E) none of these

Accepted Answer

The formula to calculate time when acceleration and final velocity are known is $t = \frac{v}{a}$, where $v$ is the final velocity (30 m/s) and $a$ is the acceleration (2 m/s^2). Plugging in the values, $t = \frac{30}{2} = 15$ seconds.

Question 14

The two measurements necessary for calculating average speed are
A) velocity and time.
B) distance and acceleration.
C) distance and time.
D) velocity and distance.
E) acceleration and time.

Accepted Answer

Average speed is calculated by dividing the total distance traveled by the total time taken to travel that distance.

Question 15

A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. How far below the level from which it was thrown is the rock 2 seconds later?
A) 19.6 m
B) 4.9 m
C) 14.7 m
D) 9.8 m

Accepted Answer

The answer of A man leans over the edge of...

Question 16

A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is
A) equal to its weight.
B) equal to its weight divided by its mass.
C) zero.
D) equal to the product of its mass times its weight.

Accepted Answer

If ice friction and air resistance are neglected, no force is required to keep the puck sliding at constant velocity due to Newton's first law of motion, which states that an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Question 17

A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, one second later the rock's speed is
A) zero.
B) 9.8 m/s.
C) 14.7 m/s.
D) 4.9 m/s.
E) none of the above.

Accepted Answer

The answer of A man leans over the edge of...

Question 18

Consider drops of water that leak at a steady rate from a dripping faucet. As the drops fall they
A) get closer together.
B) remain at a relatively fixed distance from one another.
C) get farther apart.

Accepted Answer

As the drops fall, they accelerate due to gravity. Since each subsequent drop starts its fall slightly later, the first drop always has a head start and thus accelerates for a longer time compared to the drops that follow. This causes the drops to get farther apart as they fall.

Question 19

An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of about
A) 20 m/s.
B) 15 m/s.
C) 5 m/s.
D) 10 m/s.
E) not enough information given to estimate

Accepted Answer

Using the equation of motion $ v^2 = u^2 + 2gh $, where $ u = 0 $ (initial velocity), $ g = 9.8 \, \text{m/s}^2 $, and $ h = 5 \, \text{m} $, we find $ v \approx 10 \, \text{m/s} $.

Question 20

At one instant an object in free fall is moving downward at 50 meters per second. One second later its speed should be about
A) 100 m/s.
B) 55 m/s.
C) 50 m/s.
D) 25 m/s.
E) 60 m/s.

Accepted Answer

In free fall, an object accelerates downward at approximately 9.8 m/s². After one second, its speed increases by about 9.8 m/s, so 50 m/s + 9.8 m/s ≈ 60 m/s.

Quiz 3: Equilibrium and Linear Motion

Twelve seconds after starting from rest, an object falling freely will have a speed of

Disregarding air resistance, objects fall with constant

A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before Striking the water

A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always

Galileo's use of inclined planes allowed him to effectively

While an object near the earth's surface is in free fall , its

An object falls freely from rest on a planet where the acceleration due to gravity is twice as much as it is on Earth. In the first 5 seconds it falls a distance of

If a rocket initially at rest accelerates at a rate of 50 m/s2 for one minute, its speed will be

If a car accelerates from rest at 2 meters per second per second, its speed 3 seconds later will be about

A pot falls from a ledge and hits the ground 45 m below. The speed with which it hits the ground is

If a projectile is fired straight up at a speed of 10 m/s, the total time to return to its starting position is about

Disregarding air drag, how fast must you toss a ball straight up in order for it to take 2 seconds to return to the level from which you tossed it?

A car accelerates at 2 meters per second per second. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 30 m/s?

The two measurements necessary for calculating average speed are

A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. How far below the level from which it was thrown is the rock 2 seconds later?

A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is

A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, one second later the rock's speed is

Consider drops of water that leak at a steady rate from a dripping faucet. As the drops fall they

An apple falls from a tree and hits the ground 5 meters below. It hits the ground with a speed of about

At one instant an object in free fall is moving downward at 50 meters per second. One second later its speed should be about