Question 1

A car is traveling in the negative x-direction at 25 m/s. The car slows down to 10 m/s over a period of 5 seconds as it keeps going in the negative x-direction. What is the car's average acceleration over this period?

Accepted Answer

$$+3\ \mathrm{m/s^2$}$$

Question 2

Which of the following statements about constant acceleration is TRUE?

Accepted Answer

If acceleration is constant, the average acceleration is equal to the instantaneous acceleration.

Question 3

A bird is flying along the x-axis. Its position as a function of time is given by $$x = 15t - 3t^2$. In what direction is the bird flying at time t = 5$ s?

Accepted Answer

In the negative x-direction.

Question 4

Which equation would you use to find the velocity of a car after 8 s, if it starts at $$20\ \mathrm{m/s} in $$the positive x-direction with a constant acceleration of $$-3\ \mathrm{m/s^2$}$$?

Accepted Answer

$$v_x = v_{0x} + a_x t$$

Question 5

A motorcyclist is moving at a constant speed of $$20.0\ \mathrm{m/s}$$ and passes a police car at rest. The police car starts pursuing with an acceleration of $$4.0\ \mathrm{m/s^2$}. $$How much time elapses until the police car catches up?

Accepted Answer

$$10\ \mathrm{s}$$

Question 6

Which of the following is the correct equation for the position of an object under constant acceleration?

Accepted Answer

$$x(t) = x_0$ + v_{0x} t + \frac{1}{2} a_x t^2$

Question 7

A ball is thrown straight upward with an initial speed of $$15.0\ \mathrm{m/s}$$ from the top of a $$50.0\ \mathrm{m}$$ building. If you were to use only one equation to find the maximum height above ground the ball reaches, which would it be?

Accepted Answer

$$v_y^2$ = v_{0y}^2 + 2 a_y \Delta y$$

Question 8

For an object in free fall near the Earth's surface, what is the value and direction of its acceleration (ignoring air resistance)?

Accepted Answer

$$a = -9.8\ \mathrm{m/s^2$}$$, downward

Question 9

Which of the following best describes the motion of an object if its velocity and acceleration are in opposite directions?

Accepted Answer

The object is slowing down.

Question 10

Which of the following is NOT a correct equation of motion for constant acceleration?

Accepted Answer

$$x = x_0$ + a_x t$$

Question 11

A car moves with a constant velocity of $$15\ \mathrm{m/s}$$ for $$10\ \mathrm{s}. $$What is the displacement of the car?

Accepted Answer

$$150\ \mathrm{m}$$

Question 12

If the velocity of an object is given by $$v_x = 10 - 2t$$, what is the acceleration of the object?

Accepted Answer

$$-2\ \mathrm{m/s^2$}$$

Question 13

Which of the following is a correct method to determine position as a function of time if velocity is known as a function of time?

Accepted Answer

$$x(t) = \int v_x(t) dt$$

Question 14

A ball is thrown vertically upward. At the highest point of its trajectory (ignoring air resistance), which of the following is true?

Accepted Answer

The velocity is zero and the acceleration is $$-g.$$

Question 15

A car starts from rest and accelerates at $$2\ \mathrm{m/s^2$}$$ for $$5\ \mathrm{s}. $$What is its final velocity?

Accepted Answer

$$10\ \mathrm{m/s}$$

Question 16

Which of the following graphs best represents the velocity vs. time for a ball thrown straight up and then falling back down (ignoring air resistance)?

Accepted Answer

A straight line with negative slope crossing the time axis.

Question 17

A car moves in the positive x-direction with a constant acceleration. Which of the following equations gives the relationship between its velocity and displacement?

Accepted Answer

$$v_x^2$ = v_{0x}^2 + 2 a_x \Delta x$$

Linear Motion with Constant Acceleration & Free Fall in 1D (PHY 121 - University Physics I)

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