Question 1

A v-t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 6 s the acceleration of the ball is zero. We know that at t = 6 s,

Accepted Answer

If the acceleration of the ball is zero, then the velocity of the ball is constant. Therefore, the curve is not changing at t = 6 s and the velocity of the ball is not changing. The slope of the curve may or may not be zero, and the curve may or may not cross the time axis. The curve is not at v = 0, t = 0, since it starts at the origin, not at (0,0) specifically.

Question 2

An x-t graph is drawn for a ball moving in one direction. The graph starts at the origin and at t = 6 s the velocity of the ball is zero. We can be positive that at t = 6 s,

Accepted Answer

The answer of An x-t graph is drawn for a...

Question 3

A European sports car dealer claims that his product will accelerate at a constant rate from rest to a speed of 100 km/hr in 8.00 s. What is the speed after the first 5.00 s of acceleration? (Hint: First convert the speed to m/s.)

Accepted Answer

The final speed is 100 km/hr, which is 27.8 m/s. The acceleration is 27.8 m/s divided by 8 s, which is 3.475 m/s². After 5 s, the speed is 3.475 m/s² * 5 s = 17.4 m/s.

Question 4

A bird, accelerating from rest at a constant rate, experiences a displacement of 37 m in 11 s. What is its acceleration?

Accepted Answer

The answer of A bird, accelerating from rest at a...

Question 5

An object, initially moving in the negative x direction, is subjected to a change in velocity in the negative y direction. If the resulting velocity vector is drawn from the origin, into which quadrant does this vector point?

Accepted Answer

The initial velocity is in the negative x direction, and the change in velocity is in the negative y direction. The resulting velocity vector will have components in both the negative x and negative y directions, placing it in the 3rd quadrant.

Question 6

A strobe photograph of a car moving along a straight road shows the interval between each successive image to be diminishing. If the direction of motion of the car is taken as positive, which of the following are negative?

Accepted Answer

When the interval between each successive image is diminishing, it means that the car is slowing down. Therefore, its speed and average velocity are decreasing, which makes them negative. However, its acceleration is positive because it is slowing down, which means that its velocity is changing in the negative direction. Therefore, the correct choice is C, the average acceleration of the car.

Question 7

A particle moves east at constant velocity  for a time interval  t. It then moves north at a constant velocity, with the same speed as before, for another time interval  t Finally it moves east again with the original velocity. At the instant an additional time interval  t has elapsed, which of the following are true about the average velocity and the average acceleration for the motion described?

Accepted Answer

The answer of A particle moves east at constant velocity...

Question 8

A 50-g ball traveling at 25.0 m/s is bounced off a brick wall and rebounds at 20.0 m/s. A high-speed camera records this event. If the ball is in contact with the wall for 3.50 ms, what is the magnitude of the average acceleration of the ball during this time interval?

Accepted Answer

Using the formula $a=\frac{\Delta v}{\Delta t}$, we can calculate the average acceleration of the ball during the 3.50 ms contact time:

$a=\frac{20.0-(-25.0)}{3.50	imes10^{-3}}=\frac{45.0}{3.50	imes10^{-3}}=12,857.14 \approx 12,900	ext{ m/s}^2$

Therefore, the correct answer is D.

Question 9

The slope of the acceleration-time curve represents:

Accepted Answer

The slope of the acceleration-time curve represents the rate of change of acceleration. It shows how quickly the acceleration is changing over time.

Question 10

The value of an object's acceleration may be characterized in equivalent words by which of the following?

Accepted Answer

The value of an object's acceleration is the rate of change of velocity, which is why choice D, "rate of change of velocity," is the best choice. Displacement (choice A) and rate of change of displacement (choice B) are both measures of an object's distance traveled, rather than its acceleration. Velocity (choice C) is the rate of change of displacement, rather than the rate of change of velocity, and is therefore also not a measure of acceleration.

Question 11

A ball is pushed downhill with an initial velocity of 3.0 m/s. The ball rolls down a hill with a constant acceleration of 1.6 m/s². The ball reaches the bottom of the hill in 6.0 s. What is the ball's velocity at the bottom of the hill?

Accepted Answer

The ball's velocity at the bottom of the hill can be calculated using the formula $v = u + at$, where $v$ is the final velocity, $u$ is the initial velocity (3.0 m/s), $a$ is the acceleration (1.6 m/s$^2$), and $t$ is the time (6.0 s). Plugging in the values, we get $v = 3.0 m/s + (1.6 m/s^2 \times 6.0 s) = 3.0 m/s + 9.6 m/s = 12.6 m/s$, which rounds to 13 m/s.

Question 12

An object moves at a constant velocity of 12 m/s to the southwest for an interval of 20 s. Halfway through this interval, what is the magnitude of its instantaneous velocity?

Accepted Answer

Since the object is moving at a constant velocity to the southwest, its velocity vector remains the same throughout the interval. Therefore, halfway through the interval (after 10 seconds) its velocity will still be 12 m/s to the southwest. The magnitude of this velocity vector is still 12 m/s since its direction hasn't changed. Therefore, choice C is correct.

Question 13

A car is initially moving at 30 m/s east and a little while later it is moving at 10 m/s north. Which of the following best describes the orientation of the average acceleration during this time interval?

Accepted Answer

The answer of A car is initially moving at 30...

Question 14

A strobe photograph shows equally spaced images of a car moving along a straight road. If the time intervals between images is constant, which of the following cannot be positive?

Accepted Answer

The answer of A strobe photograph shows equally spaced images...

Question 15

A bird, accelerating from rest at a constant rate, experiences a displacement of 37 m in 11 s. What is the final velocity after 11 s?

Accepted Answer

The answer of A bird, accelerating from rest at a...

Question 16

A European sports car dealer claims that his car will accelerate at a constant rate from rest to 100 km/hr in 8.00 s. If so, what is the acceleration? (Hint: First convert speed to m/s.)

Accepted Answer

To find the acceleration, first convert 100 km/hr to m/s: 100 km/hr = 100,000 m/3600 s = 27.78 m/s. Then use the formula for acceleration: a = (final velocity - initial velocity) / time = (27.78 m/s - 0 m/s) / 8.00 s = 3.47 m/s².

Question 17

An object is dropped from a height. Once it is moving, which of the following statements is true, at least at one point?

Accepted Answer

Velocity and acceleration are measured in different units (velocity in meters per second, acceleration in meters per second squared), so they cannot be directly compared or equal.

Question 18

In the case of constant acceleration, the average velocity equals the instantaneous velocity:

Accepted Answer

When acceleration is constant, the average velocity is equal to the instantaneous velocity at the midpoint of the time interval. This is because, in uniform acceleration, the velocity changes linearly over time, making the average velocity (initial velocity + final velocity)/2 equal to the instantaneous velocity at the midpoint.

Question 19

A hiker walks 200 m east and then walks 100 m north. In what direction is her resulting displacement?

Accepted Answer

The answer of A hiker walks 200 m east and...

Question 20

The first displacement is 7 m and the second displacement is 3 m. They cannot add together to give a total displacement of:

Accepted Answer

The answer of The first displacement is 7 m and...

Quiz 2: Motion, Forces, and Newtons Laws