Q: Which equation correctly represents Newton's second law in vector form?

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

Question 1

Which of the following best distinguishes kinematics from dynamics in the study of motion?

Accepted Answer

Kinematics describes how objects move, while dynamics explains why they move.

Question 2

A ball is initially at rest on the floor of a bus. Suddenly, the ball starts rolling towards the rear of the bus. What is the most likely explanation for this observation?

Accepted Answer

The bus is accelerating forward.

Question 3

According to Newton's first law, what happens to an object if the net external force acting on it is zero?

Accepted Answer

It will maintain its current state of motion (rest or constant velocity).

Question 4

Which equation correctly represents Newton's second law in vector form?

Accepted Answer

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

Question 5

A 10 kg box is at rest on a horizontal surface. If the net force acting on the box is zero, what can you conclude about the box's motion?

Accepted Answer

The box is at rest or moving at constant velocity.

Question 6

A 5 kg object is acted upon by a net force of 20 N. What is its acceleration?

Accepted Answer

$$a = 4\ 	ext{m/s}^2$$

Question 7

Which of the following is an example of Newton's third law?

Accepted Answer

A swimmer pushes water backward and moves forward.

Question 8

A 2 kg mass is suspended by a rope from the ceiling. What is the tension in the rope if the mass is at rest? (Assume $$g = 9.8\ 	ext{m/s}^2)$$

Accepted Answer

$$T = 19.6\ 	ext{N}$$

Question 9

In a tug-of-war, Team A pulls with a force of 100 N to the right, and Team B pulls with a force of 100 N to the left. What is the net force on the rope?

Accepted Answer

0 N

Question 10

A ring is suspended by three ropes: one vertical and two at $$60^\circ to $$the horizontal on either side. If the mass hanging from the ring is $$m$$, what is the tension in each of the angled ropes?

Accepted Answer

$$T = \frac{mg}{2\sin 60^\circ}$$

Question 11

Which of the following statements about the normal force is correct?

Accepted Answer

The normal force is a reaction force that acts perpendicular to the surface.

Question 12

A 50 kg person stands on a scale in an elevator that is accelerating upward at $$2\ 	ext{m/s}^2. $$What does the scale read?

Accepted Answer

$$590\ 	ext{N}$$

Question 13

Which of the following is NOT a fundamental force of nature?

Accepted Answer

Frictional force

Question 14

The gravitational force between two masses $$M$$ and $$m$$ separated by distance $$r is $$given by:

Accepted Answer

$$F = \frac{GMm}{r^2$}$$

Question 15

If the net force on a 3 kg object is zero, which of the following must be true?

Accepted Answer

The object is moving at constant velocity or at rest.

Question 16

A frog sits on a lily pad. The lily pad pushes up on the frog with a normal force. According to Newton's third law, what is the reaction force?

Accepted Answer

The frog pushes down on the lily pad with an equal and opposite force.

Question 17

A 1 kg object is dropped from rest near the Earth's surface. Neglecting air resistance, what is the net force acting on the object?

Accepted Answer

$$9.8\ 	ext{N}$$ downward

Question 18

A car of mass 1000 kg accelerates from rest to $$20\ 	ext{m/s} in 10 $$seconds. What is the average net force acting on the car?

Accepted Answer

$$2000\ 	ext{N}$$

Question 19

Which of the following best describes inertia?

Accepted Answer

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

Question 20

A 10 kg mass is hanging from two ropes, each making a $$45^\circ$$ angle with the ceiling. What is the tension in each rope? (Use $$g = 9.8\ 	ext{m/s}^2)$$

Accepted Answer

$$T = \frac{10 	imes 9.8}{2 \sin 45^\circ} = 69.3\ 	ext{N}$$

Forces and Motion: Newton's Laws and Applications (Physics 211, Module 06)

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