Question 1

A ball is thrown upward from the top of a 50.0 m building with an initial speed of 15.0 m/s. What is the maximum height above the ground that the ball reaches? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$61.5\ \mathrm{m}$$

Question 2

Which equation correctly describes the position of an object moving in 1D with constant acceleration?

Accepted Answer

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

Question 3

A projectile is launched at an angle $$	heta$$ above the horizontal with initial speed $$v_0. $$What is the initial vertical component of velocity?

Accepted Answer

$$v_{0y} = v_0$ \sin 	heta$$

Question 4

At what point in its trajectory does a projectile launched above the horizontal reach its minimum speed (neglecting air resistance)?

Accepted Answer

At the highest point of the trajectory

Question 5

A girl runs in a park with her position given by $$\vec{r} = b t^2$ \hat{i} - c t \hat{j}$$, where $$b = 2.00\ \mathrm{m/s^2$}$$ and $$c = 9.00\ \mathrm{m/s}. $$What is her acceleration vector?

Accepted Answer

$$\vec{a} = 4.00\ \mathrm{m/s^2$} \hat{i}$$

Question 6

A projectile is shot from a cliff 115 m above ground level with an initial speed of 65.0 m/s at an angle of 35.0° above the horizontal. What is the range of the projectile?

Accepted Answer

$$530.4\ \mathrm{m}$$

Question 7

Which of the following best describes the acceleration of a projectile (neglecting air resistance)?

Accepted Answer

It is constant and directed downward throughout the motion

Question 8

An airplane moving with constant horizontal velocity of $$40.0\ \mathrm{m/s}$$ drops a package from $$100\ \mathrm{m}$$ above ground. How far ahead horizontally should the airplane be before dropping the package so it lands at the desired location?

Accepted Answer

$$180\ \mathrm{m}$$

Question 9

Which equation gives the displacement vector $$\Delta \vec{r}$$ between two positions $$\vec{r}_1$$ and $$\vec{r}_2$$?

Accepted Answer

$$\Delta \vec{r} = \vec{r}_2 - \vec{r}_1$$

Question 10

A destroyer simultaneously fires two shells with the same initial speed at two different enemy ships. The shells follow different trajectories. Which ship gets hit first (neglect air resistance)?

Accepted Answer

Enemy 1 (the closer ship)

Question 11

If you set the cruise control of your car to a certain speed and take a turn while on cruise control, is the car accelerating?

Accepted Answer

Yes

Question 12

Which formula correctly expresses the average velocity vector in terms of displacement and time interval?

Accepted Answer

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

Question 13

For symmetric projectile motion, what is the total time of flight if the initial vertical velocity is $$v_{0y}$$ and acceleration due to gravity is $$g$$?

Accepted Answer

$$t = \frac{2 v_{0y}}{g}$$

Question 14

A projectile is launched at an angle above the horizontal. At which point is its acceleration greatest (neglecting air resistance)?

Accepted Answer

The acceleration is the same (but nonzero) at all points along the trajectory

Question 15

Which equation describes the instantaneous velocity vector in 2D motion?

Accepted Answer

$$\vec{v} = \frac{d\vec{r}}{dt} = v_x \hat{i} + v_y \hat{j}$$

Question 16

A package is dropped from an airplane moving horizontally at constant velocity. What is the shape of the package's trajectory (neglecting air resistance)?

Accepted Answer

Parabolic

Question 17

Which of the following is true about the horizontal and vertical motions of a projectile?

Accepted Answer

They are independent of one another

Question 18

Given the position vector $$\vec{r} = x \hat{i} + y \hat{j} + z \hat{k}$$, which of the following correctly expresses the displacement between two points?

Accepted Answer

$$\Delta \vec{r} = (x_2$ - x_1$) \hat{i} + (y_2$ - y_1$) \hat{j} + (z_2$ - z_1$) \hat{k}$$

Question 19

A projectile is launched horizontally from a height $$h$$ with initial speed $$v_0. $$What is the time it takes to hit the ground?

Accepted Answer

$$t = \sqrt{\frac{2h}{g}}$$

Quantities of 2D Motion and Projectile Motion (Chapter 3 Study Notes)

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