Question 1

A volcano ejects a rock straight upward at $$30\ \mathrm{m/s}. $$Neglecting air resistance, how long does it take for the rock to reach its maximum height?

Accepted Answer

$$3.1\ \mathrm{s}$$

Question 2

Using the same volcano scenario, what is the maximum height reached by the rock, relative to its starting position? (Initial velocity $$v_0 = 30$$\ \mathrm{m/s}$$, a = -9.8$$\ \mathrm{$$m/s^2$$}$$)

Accepted Answer

$$45.9\ \mathrm{m}$$

Question 3

Which of the following best describes Newton's First Law?

Accepted Answer

An object at rest will remain at rest, and an object in motion will continue in motion at constant velocity unless acted upon by a net force.

Question 4

A sled is moving on a slick surface. What will happen to its motion if no one pushes it and friction is negligible?

Accepted Answer

It will continue moving at constant speed in a straight line.

Question 5

Which of the following is the correct definition of force?

Accepted Answer

A vector quantity that causes an object to change its motion (speed and/or direction).

Question 6

A briefcase is being lifted upward at constant speed. Which statement about the forces acting on it is correct?

Accepted Answer

The upward force is equal to the downward force.

Question 7

An elevator moves downward at constant speed in a tall building. How does the magnitude of the upward force exerted by the cable compare to the magnitude of the downward force exerted by Earth on the elevator?

Accepted Answer

The upward force is equal to the downward force.

Question 8

Which of the following is a correct statement about mass?

Accepted Answer

Mass is a scalar quantity and depends on the amount and type of matter.

Question 9

A cannonball is fired horizontally from a cliff. Which force diagram correctly represents the forces acting on the cannonball immediately after it leaves the cannon (neglecting air resistance)?

Accepted Answer

A single downward arrow labeled $$F_{gravity}.$$

Question 10

Which equation would you use to calculate the maximum height $$h$$ reached by an object thrown vertically upward with initial velocity $$v_0$$ and acceleration $$a$$?

Accepted Answer

$$v^2$$ = $$v_0^2 + 2 a h$

Question 11

A student claims that a force is needed to keep an object moving at constant velocity. Which law or principle refutes this claim?

Accepted Answer

Newton's First Law

Question 12

If two blocks of copper have masses $$m_1$$ and $$m_2$$, what is their combined mass?

Accepted Answer

$$m_1$$ + $$m_2$$

Question 13

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

Accepted Answer

newton (N)

Question 14

A rock is thrown straight up with initial velocity $$v_0. At $$its maximum height, which of the following is true?

Accepted Answer

Its velocity is zero and its acceleration is $$-9.8\ \mathrm{m/s^2$}.$$

Question 15

Which of the following best describes a free-body diagram?

Accepted Answer

A diagram showing all the forces acting on an object, represented as arrows.

Question 16

A space probe is drifting in deep space, far from any stars or planets, with all its engines off. What will happen to its motion?

Accepted Answer

It will continue moving at constant velocity.

Question 17

Which of the following is a contact force?

Accepted Answer

Friction

Question 18

A student draws a free-body diagram for a book resting on a table. Which forces should be included?

Accepted Answer

Gravity and the normal force from the table.

Question 19

Which of the following statements about net force is correct?

Accepted Answer

Net force is the vector sum of all external forces acting on an object.

Interactions and Forces: Newton's First Law, Free Fall, and Force Diagrams

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