Q: Which of the following best describes the range $$R of a $$projectile launched at speed $$v_0$$ and angle $$\theta$$ above the horizontal (neglecting air resistance)?

$$R = \frac{v_0$^2 \sin 2\theta}{g}$$

Q: Which of the following is the correct expression for Newton's second law?

$$\vec{F}_{\text{net}} = m \vec{a}$$

Question 1

A dart is launched with a speed of 16.0 m/s at an angle of 30.0° above the horizontal. How many seconds elapse until the dart travels a horizontal distance of 4.0 m? Neglect air resistance.

Accepted Answer

$$t = \frac{4.0}{16.0 \cos 30.0^\circ}$$

Question 2

A monkey is hanging from a branch. A scientist aims a dart gun directly at the monkey and fires. The monkey lets go at the instant the dart is fired. Neglecting air resistance, what happens?

Accepted Answer

The dart will hit the monkey because both fall with the same acceleration due to gravity.

Question 3

Which of the following best describes the range $$R of a $$projectile launched at speed $$v_0$$ and angle $$	heta$$ above the horizontal (neglecting air resistance)?

Accepted Answer

$$R = \frac{v_0$^2 \sin 2	heta}{g}$$

Question 4

What happens to the range of a projectile as the launch angle $$	heta$$ approaches $$90^\circ$$, assuming constant initial speed and neglecting air resistance?

Accepted Answer

The range approaches zero.

Question 5

A force is a vector quantity. Which of the following statements is true about forces?

Accepted Answer

A force has both magnitude and direction.

Question 6

Two crewpersons pull a raft. Crewperson 1 pulls with a force of 130 N at an angle of 34° counterclockwise from the negative x-axis. Crewperson 2 pulls at an angle of 45° clockwise from the negative x-axis. What force should Crewperson 2 apply so that the total force is in the positive x-direction?

Accepted Answer

$$F_2 = 130$$ \frac{\cos 34^\circ}{\cos 45^\circ}$$

Question 7

Which of the following is a long-range force?

Accepted Answer

Gravitational force

Question 8

A sledder pushes her sled across a horizontal snow surface and then jumps in. The sled gradually slows to a halt. Which force is responsible for slowing the sled?

Accepted Answer

Kinetic friction

Question 9

According to Newton's first law, what happens to an object in an inertial reference frame if no net force acts on it?

Accepted Answer

It remains at rest or moves at constant velocity.

Question 10

A car is moving on a frictionless icy road and tries to turn. What will happen?

Accepted Answer

The car will continue in a straight line due to lack of friction.

Question 11

Which of the following is the correct expression for Newton's second law?

Accepted Answer

$$\vec{F}_{	ext{net}} = m \vec{a}$$

Question 12

Which of the following is NOT a contact force?

Accepted Answer

Gravitational force

Question 13

A person is stranded on a frictionless icy lake. To reach the shore, they throw their boot. In which direction should they throw the boot to move most quickly toward the shore?

Accepted Answer

Away from the shore

Question 14

Which of the following statements about Newton's third law is correct?

Accepted Answer

For every action, there is an equal and opposite reaction.

Question 15

According to Newton's law of gravity, what is the gravitational force between two objects of masses $$m_1$$ and $$m_2$$ separated by distance $$r$$?

Accepted Answer

$$F = G \frac{m_1$ m_2$}{r^2$}$$

Question 16

If the distance between two planets is doubled, what happens to the gravitational force between them?

Accepted Answer

It becomes one quarter as strong.

Question 17

A box is acted on by a net force in the positive x-direction. Which statement is always true?

Accepted Answer

The acceleration must be in the +x-direction.

Question 18

Which force is always perpendicular to the surface an object is pressing against?

Accepted Answer

Normal force

Question 19

A spring is compressed. What type of force does it exert on an object in contact with it?

Accepted Answer

A pushing force

Question 20

A projectile is launched at an angle $$	heta$$ with initial speed $$v_0. $$What is the formula for its maximum height?

Accepted Answer

$$H = \frac{v_0$^2 \sin^2$ 	heta}{2g}$$

Projectile Motion: Concepts, Equations, and Applications

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