Question 1

A cannon fires a cannonball, as shown in the first image. According to Newton's third law, what happens to the cannon when the cannonball is launched?

Accepted Answer

The cannon recoils backward with a force equal in magnitude and opposite in direction to the force on the cannonball.

Question 2

A skydiver reaches terminal velocity, as depicted in the second image. Which statement best describes the forces acting on the skydiver at this point?

Accepted Answer

The force of gravity is equal in magnitude and opposite in direction to the air resistance.

Question 3

A rocket launches upward, as shown in the third image. Which of Newton's laws best explains the rocket's motion?

Accepted Answer

Newton's second law, because the rocket's acceleration depends on the net force and its mass.

Question 4

Which equation correctly expresses Newton's second law of motion?

Accepted Answer

$$\Sigma F = ma$$

Question 5

A 10 kg box is at rest on a horizontal surface. What is the magnitude of the gravitational force acting on the box? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$98\ \mathrm{N}$$

Question 6

Which of the following best describes the center of mass (CM) of an object?

Accepted Answer

The point where all the mass of the object can be considered to be concentrated for analysis of motion.

Question 7

A person stands in an elevator that accelerates upward. How does the apparent weight of the person compare to their actual weight?

Accepted Answer

The apparent weight is greater than the actual weight.

Question 8

Which of the following is a vector quantity?

Accepted Answer

Force

Question 9

A box is pushed to the right across a rough surface. Which direction does the friction force act?

Accepted Answer

To the left

Question 10

A 5 kg object is acted on by a net force of $$20\ \mathrm{N}. $$What is its acceleration?

Accepted Answer

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

Question 11

Which trigonometric function would you use to find the component of a force along the surface if you know the angle $$	heta$$ between the force and the surface and the magnitude of the force?

Accepted Answer

$$\cos 	heta$$

Question 12

Which of the following statements about equilibrium is correct?

Accepted Answer

An object in equilibrium has zero net force acting on it.

Question 13

A 2 kg object is hanging from a rope. What is the tension in the rope if the object is at rest? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$19.6\ \mathrm{N}$$

Question 14

Which of the following best explains why astronauts in orbit feel weightless?

Accepted Answer

They are in free fall, accelerating toward Earth at the same rate as their spacecraft.

Question 15

A box is pulled with a force of $$30\ \mathrm{N} at an $$angle of $$60^\circ$$ above the horizontal. What is the horizontal component of the force?

Accepted Answer

$$30 	imes \cos 60^\circ$$

Question 16

Which of the following is NOT a correct statement of Newton's laws?

Accepted Answer

The net force on an object is always zero.

Question 17

A person leans forward when carrying a heavy backpack. Why is this necessary?

Accepted Answer

To keep the center of mass over the area of support and maintain stability.

Question 18

Which of the following is a correct unit for force?

Accepted Answer

Newton

Question 19

A 50 kg person stands on a scale in an elevator accelerating downward at $$2\ \mathrm{m/s^2$}. $$What does the scale read? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$390\ \mathrm{N}$$

Question 20

Which of the following best describes the difference between mass and weight?

Accepted Answer

Mass is the amount of matter in an object, weight is the force due to gravity acting on that mass.

Center of Mass and Forces: Newton’s Laws and Applications

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