Q: If the gravitational field strength on the Moon is $$1/6$$ that of Earth, what is the weight of a 12 kg object on the Moon?

$$W = mg_{moon} = 12 \times \frac{9.8}{6} = 19.6\ \mathrm{N}$$

Q: A 5 kg box is at rest on a horizontal table. What is the magnitude of the normal force exerted by the table?

$$F_N = mg = 5 \times 9.8 = 49\ \mathrm{N}$$

Question 1

According to Newton's first law, what will happen to a hockey puck sliding on perfectly frictionless ice after being struck by a stick?

Accepted Answer

It will continue moving at a constant velocity indefinitely.

Question 2

Which of the following best describes inertia as defined by Newton?

Accepted Answer

The tendency of an object to resist changes in its motion.

Question 3

A 2 kg object is acted upon by a net force of 10 N. What is its acceleration?

Accepted Answer

$$a = \frac{F_{net}}{m} = \frac{10}{2} = 5\ \mathrm{m/s^2$}$$

Question 4

Which force is responsible for keeping a book stationary on a table?

Accepted Answer

The normal force exerted by the table upward.

Question 5

A block is pulled horizontally across a rough surface at constant speed. Which statement is true about the forces acting on the block?

Accepted Answer

The net force on the block is zero.

Question 6

If the gravitational field strength on the Moon is $$1/6$$ that of Earth, what is the weight of a 12 kg object on the Moon?

Accepted Answer

$$W = mg_{moon} = 12 	imes \frac{9.8}{6} = 19.6\ \mathrm{N}$$

Question 7

Which of the following is a long-range force?

Accepted Answer

Gravity between the Earth and the Moon.

Question 8

A compressed spring exerts a force on an object. Which equation describes the magnitude of this force?

Accepted Answer

$$F = kx$$

Question 9

A car suddenly stops and you feel thrown forward. This is best explained by:

Accepted Answer

Newton's first law and inertia.

Question 10

Which of the following statements about mass and weight is correct?

Accepted Answer

Weight depends on gravitational field strength, while mass is intrinsic to the object.

Question 11

A 5 kg box is at rest on a horizontal table. What is the magnitude of the normal force exerted by the table?

Accepted Answer

$$F_N = mg = 5 	imes 9.8 = 49\ \mathrm{N}$$

Question 12

Which scenario best illustrates Newton's first law in a real-world context?

Accepted Answer

A coin tossed inside a moving train lands in your hand, even as the train moves forward.

Question 13

A block is pulled by a rope with a force of 20 N to the right, while friction exerts a force of 15 N to the left. What is the net force and direction?

Accepted Answer

$$F_{net} = 20 - 15 = 5\ \mathrm{N} to $$the right

Question 14

Which force opposes the motion of an object sliding across a surface?

Accepted Answer

Kinetic friction

Question 15

A jet airplane is propelled upward during takeoff by which force?

Accepted Answer

Thrust force

Question 16

Which of the following is NOT a contact force?

Accepted Answer

Gravity

Question 17

A 10 kg object is suspended by a rope. What is the tension in the rope if the object is at rest?

Accepted Answer

$$T = mg = 10 	imes 9.8 = 98\ \mathrm{N}$$

Question 18

Which statement about Aristotle's view of motion is correct?

Accepted Answer

He believed that heavier objects fall faster than lighter ones.

Question 19

A ball is dropped from a tree on a moving Earth. Why does it land directly below the branch?

Accepted Answer

Because the ball, branch, and air all share the Earth's motion due to inertia.

PHYSICS 1051 – Chapter 5: Force and Motion (Study Notes)

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