Q: A person pushes against a wall with a force of $$50\ \text{N}. $$According to Newton’s Third Law, what is the force exerted by the wall on the person’s hand?

$$50\ \text{N}$$, in the opposite direction

Q: A cannon fires a cannonball. If the cannonball has mass $$m$$ and the cannon has mass $$M$$, and both experience a force $$F$$ for the same duration, what is the ratio of their accelerations?

$$\dfrac{a_{\text{cannonball}}}{a_{\text{cannon}}} = \dfrac{M}{m}$$

Question 1

A person pushes against a wall with a force of $$50\ 	ext{N}. $$According to Newton’s Third Law, what is the force exerted by the wall on the person’s hand?

Accepted Answer

$$50\ 	ext{N}$$, in the opposite direction

Question 2

A boxer punches a heavy bag and a sheet of tissue paper in midair with the same motion. Why is the force on the tissue paper much less than on the bag?

Accepted Answer

The tissue paper can only exert a small force back, limiting the force the boxer can apply

Question 3

A rocket accelerates in space by ejecting exhaust gases backward. Which statement best explains this phenomenon?

Accepted Answer

The rocket recoils from the exhaust gases, which exert an equal and opposite force on the rocket

Question 4

A bus and a bug collide head-on. Which statement is true regarding the forces during the collision?

Accepted Answer

The force exerted by the bug on the bus equals the force exerted by the bus on the bug

Question 5

A cannon fires a cannonball. If the cannonball has mass $$m$$ and the cannon has mass $$M$$, and both experience a force $$F$$ for the same duration, what is the ratio of their accelerations?

Accepted Answer

$$\dfrac{a_{	ext{cannonball}}}{a_{	ext{cannon}}} = \dfrac{M}{m}$$

Question 6

A person stands on an inclined plane. Which component of the gravitational force increases as the angle of the incline increases?

Accepted Answer

The parallel component $$mg_{\parallel}$$

Question 7

A helicopter hovers by pushing air molecules downward. What is the reaction force responsible for lift?

Accepted Answer

The upward force exerted by the air molecules on the helicopter

Question 8

A car accelerates forward because its tires push backward on the road. What is the reaction force according to Newton’s Third Law?

Accepted Answer

The road pushes forward on the tires

Question 9

A person hangs from two ropes at equal angles to the vertical. As the angle increases, what happens to the tension in each rope?

Accepted Answer

The tension increases and approaches infinity as the ropes become horizontal

Question 10

A block rests on an inclined plane. If the friction force equals the parallel component of gravity, what is the block’s acceleration?

Accepted Answer

$$a = 0$$

Question 11

Which statement best describes why action-reaction forces do not cancel each other out?

Accepted Answer

They act on different objects, so each object experiences a net force

Question 12

A falling boulder and the Earth exert equal and opposite gravitational forces on each other. Why does the boulder accelerate more than the Earth?

Accepted Answer

The boulder has much less mass, so the same force produces a greater acceleration

Question 13

In a tug-of-war, what determines which team wins?

Accepted Answer

The team that pushes harder against the ground, creating greater friction

Question 14

Which formula represents Newton’s Second Law of Motion?

Accepted Answer

$$F_{	ext{net}} = m a$$

Question 15

A projectile is launched with velocity components $$v_x$$ and $$v_y. $$Which statement is correct regarding these components?

Accepted Answer

$$v_x$$ remains constant, while $$v_y$$ changes due to gravity

Question 16

On a flat surface, what is the relationship between the normal force $$N$$ and the weight $$mg of an $$object?

Accepted Answer

$$N = mg$$

Question 17

If a system consists of both an orange and an apple, and they push against each other, why do their forces cancel?

Accepted Answer

Because the action-reaction pair is internal to the system

Question 18

Which of the following best describes inertia?

Accepted Answer

An object’s resistance to changes in motion

Question 19

A swimmer pushes water backward with her hands. What is the reaction force according to Newton’s Third Law?

Accepted Answer

The water pushes the swimmer forward

Question 20

A block slides down an incline at constant velocity. What is the relationship between friction and the parallel component of gravity?

Accepted Answer

$$f = mg_{\parallel}$$

Newton’s Third Law of Motion and Applications: Forces, Interactions, and Vectors (Chapter 5)

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