Question 1

Which of the following statements best describes Newton's First Law (Law of Inertia)?

Accepted Answer

An object will remain at rest or in uniform motion unless acted upon by a net external force.

Question 2

A block is at rest on a frictionless surface. Three forces act on it: $$\vec{F}_1 = 5\,\mathrm{N} to $$the right, $$\vec{F}_2 = 3\,\mathrm{N} to $$the left, and $$\vec{F}_3 = 2\,\mathrm{N} to $$the left. What is the net force acting on the block?

Accepted Answer

$$0\,\mathrm{N}$$

Question 3

Which of the following is a noncontact (action-at-a-distance) force?

Accepted Answer

Gravitational force

Question 4

A 2 kg object is acted upon by a net force of $$8\,\mathrm{N}. $$What is its acceleration?

Accepted Answer

$$4\,\mathrm{m/s^2$}$$

Question 5

Which of the following best illustrates Newton's Third Law (Action-Reaction)?

Accepted Answer

A swimmer pushes water backward and the water pushes the swimmer forward.

Question 6

The gravitational force between two masses $$m_1$$ and $$m_2$$ separated by a distance $$r is $$given by:

Accepted Answer

$$F_G = G\dfrac{m_1$ m_2$}{r^2$}$$

Question 7

Which statement about normal force is correct?

Accepted Answer

It always acts perpendicular to the surface of contact.

Question 8

A person pulls a rope attached to a box with a force of $$10\,\mathrm{N} to $$the right. According to Newton's Third Law, what is the force exerted by the box on the person?

Accepted Answer

$$10\,\mathrm{N} to $$the left

Question 9

In the context of tension forces in an ideal (massless, frictionless) rope passing over a pulley, which statement is true?

Accepted Answer

The tension is the same in magnitude throughout the rope.

Question 10

A block of mass $$m is $$suspended by a rope. What is the tension in the rope if the block is at rest?

Accepted Answer

$$T = mg$$

Question 11

Which of the following is NOT a direct contact force?

Accepted Answer

Gravitational force

Question 12

If the net force acting on an object is zero, which of the following must be true?

Accepted Answer

The object is moving with constant velocity or at rest.

Question 13

Two blocks are connected by a rope over a frictionless pulley. Block A has mass $$m_A$$ and block B has mass $$m_B. If$$ $$m_A \u003e m_B$$, what is the direction of acceleration?

Accepted Answer

Block A accelerates downward, Block B upward.

Question 14

Which of the following best describes inertia?

Accepted Answer

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

Question 15

A 5 kg object is pulled horizontally with a force of $$20\,\mathrm{N}. $$What is its acceleration?

Accepted Answer

$$4\,\mathrm{m/s^2$}$$

Newton’s Laws and Types of Forces — Physics 140 Study Notes

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