Question 1

A car starts from rest and accelerates at a constant rate of $$a = 15\ \mathrm{km/h^2$}$$ along a straight road. What is its velocity after $$5.0\ \mathrm{s}$$?

Accepted Answer

$$v = 75\ \mathrm{km/h}$$

Question 2

A car is moving with an initial velocity $$v_1 = 15.0$$\ \mathrm{m/s}$$ and slows down with a constant acceleration a = -2.0$$\ \mathrm{$$m/s^2$$}$$. What is its velocity after 5.0$$\ \mathrm{s}$$?

Accepted Answer

$$v_2 = 5.0$$\ \mathrm{m/s}$$

Question 3

Which of the following best describes the relationship between the sign of velocity and the sign of acceleration for an object that is slowing down?

Accepted Answer

Velocity and acceleration have opposite signs.

Question 4

Given the position-time graph of an object is a parabola opening downward, what can you say about the object's acceleration?

Accepted Answer

The object has a constant negative acceleration.

Question 5

If a car moves in the negative $$x-$$direction and its speed is decreasing, what is the sign of its acceleration?

Accepted Answer

Positive

Question 6

Which equation correctly defines the average acceleration $$a_{av}$$ over a time interval $$\Delta t$$?

Accepted Answer

$$a_{av} = \frac{\Delta v}{\Delta t}$$

Question 7

A car moves from $$x_1 to$$ $$x_2$$ along the $$x-$$axis with velocities $$v_{1x}$$ and $$v_{2x}$$, respectively. Which formula gives the average velocity?

Accepted Answer

$$v_{av} = \frac{x_2$ - x_1$}{t_2$ - t_1$}$$

Question 8

On a velocity vs. time graph, what does the slope at any point represent?

Accepted Answer

Instantaneous acceleration

Question 9

A car is moving backward (negative $$x-$$direction) and its velocity changes from $$-15.0\ \mathrm{m/s} to$$ $$-5.0\ \mathrm{m/s} in$$ $$4.0\ \mathrm{s}. $$What is its average acceleration?

Accepted Answer

$$a_{av} = +2.5\ \mathrm{m/s^2$}$$

Question 10

Which of the following statements about deceleration is correct?

Accepted Answer

Deceleration means acceleration is opposite to the direction of velocity.

Question 11

If the area under a velocity vs. time graph between $$t_1$$ and $$t_2 is $$zero, what does this imply about the object's displacement?

Accepted Answer

The object returns to its starting position.

Question 12

Which of the following is the calculus definition of instantaneous acceleration?

Accepted Answer

$$a(t) = \frac{dv}{dt} = \frac{d^2$x}{dt^2$}$$

Question 13

A car accelerates from rest with a constant acceleration. Which of the following graphs best represents its position vs. time?

Accepted Answer

A curve that gets steeper with time (parabola opening upward)

Question 14

If an object’s velocity is zero at a certain instant but its acceleration is not zero, what is the object doing?

Accepted Answer

It is changing direction.

Question 15

Which of the following best describes the net area under an acceleration vs. time graph between $$t_1$$ and $$t_2$$?

Accepted Answer

It gives the change in velocity $$\Delta v.$$

Question 16

A car is moving in the positive $$x-$$direction and speeds up. What can you say about the signs of its velocity and acceleration?

Accepted Answer

Both velocity and acceleration are positive.

Question 17

A car is moving in the negative $$x-$$direction and is speeding up. What is the sign of its acceleration?

Accepted Answer

Negative

Question 18

Which of the following is NOT a correct unit for acceleration?

Accepted Answer

$$\mathrm{m/s}$$

Acceleration and Kinematic Graphs in One-Dimensional Motion Lecture 5

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