Q: A car travels 50 m east in 24 s, then 50 m west in 48 s. What is the average speed for the entire trip?

$$\text{Average speed} = \frac{100}{72}\,\mathrm{m/s}$$

Question 1

A car moves from an initial position $$\vec{x}_i = 2\,\mathrm{m} to a $$final position $$\vec{x}_f = 10\,\mathrm{m} in 4 $$seconds. What is the displacement of the car?

Accepted Answer

$$\Delta \vec{x} = 8\,\mathrm{m}$$

Question 2

A runner completes a 50 m race in 24 s, then immediately returns to the starting point in another 48 s. What is the average velocity for the entire trip?

Accepted Answer

$$\vec{v}_{avg} = 0\,\mathrm{m/s}$$

Question 3

Which of the following best describes the difference between distance and displacement?

Accepted Answer

Distance is a scalar and measures the total path length; displacement is a vector and measures the straight-line change in position.

Question 4

A ball is thrown vertically upward from a roof with an initial velocity of $$+5\,\mathrm{m/s}$$ from a height of $$40\,\mathrm{m}. $$What is the acceleration acting on the ball during its flight?

Accepted Answer

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

Question 5

Given the position-time graph $$x(t)$$ shown, which of the following statements is correct about the velocity at $$t = 2\,\mathrm{s}$$?

Accepted Answer

The velocity is zero because the slope of $$x(t) is $$flat at $$t = 2\,\mathrm{s}.$$

Question 6

A cat starts from rest and accelerates uniformly to a velocity of $$20.11\,\mathrm{m/s} in$$ $$2\,\mathrm{s}. $$What is the acceleration?

Accepted Answer

$$a_x = 10.06\,\mathrm{m/s^2$}$$

Question 7

A truck moves with velocity $$\vec{v}_1 at $$time $$t_1$$ and $$\vec{v}_2 at $$time $$t_2. If$$ $$\vec{v}_1 is to $$the right and $$\vec{v}_2 is to $$the left, what can you say about the acceleration?

Accepted Answer

The acceleration is directed to the left.

Question 8

A car travels 50 m east in 24 s, then 50 m west in 48 s. What is the average speed for the entire trip?

Accepted Answer

$$	ext{Average speed} = \frac{100}{72}\,\mathrm{m/s}$$

Question 9

Which equation correctly gives the position $$x of an $$object under constant acceleration $$a$$ after time $$t$$, starting from $$x_0$$ with initial velocity $$v_0$$?

Accepted Answer

$$x = x_0$ + v_0$ t + \frac{1}{2} a t^2$

Question 10

A ball is thrown upward from a roof. At the top of its path, what is its velocity and acceleration?

Accepted Answer

Velocity is zero, acceleration is $$-9.8\,\mathrm{m/s^2$}$$

Question 11

A truck moves in three segments: Part 1 with $$a_1$$, Part 2 with $$a_2$$, and Part 3 with $$a_3. $$Which of the following is true about the total displacement?

Accepted Answer

Total displacement is the sum of the displacements in each part.

Question 12

If the velocity-time graph of an object is a straight line with positive slope, what does this indicate?

Accepted Answer

The object is accelerating at a constant rate.

Question 13

A car starts from rest and accelerates uniformly. After 4 seconds, it has traveled 8 meters. What is its acceleration?

Accepted Answer

$$a = 1\,\mathrm{m/s^2$}$$

Question 14

Which of the following is the correct formula for average velocity $$\vec{v}_{avg}$$?

Accepted Answer

$$\vec{v}_{avg} = \frac{\Delta \vec{x}}{\Delta t}$$

Question 15

A truck moves with constant acceleration to the left. Which of the following statements is true?

Accepted Answer

The velocity is decreasing if it was initially to the right.

Motion Along a Straight Line: Displacement, Velocity, and Acceleration

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