Q: A 200 kg crate is loaded into a 2000 kg truck. If the coefficient of static friction between the crate and the truck bed is 0.80, what is the maximum force that can be applied to the truck without the crate sliding?

The maximum force is $$F_{max} = \mu_s m_{crate} g = 0.80 \times 200 \times 9.8 = 1568\ \text{N}$$

Question 1

Which statement best describes Newton's third law as illustrated by a hammer striking a nail?

Accepted Answer

The hammer and nail exert equal and opposite forces on each other simultaneously.

Question 2

In an interaction diagram, what distinguishes internal interactions from external forces?

Accepted Answer

Internal interactions are forces between objects inside the system, while external forces are exerted by objects outside the system.

Question 3

A rocket launches by pushing hot gases downward. According to Newton's third law, what is the reaction force?

Accepted Answer

The rocket pushes the gases downward, and the gases push the rocket upward.

Question 4

When a car accelerates forward, which force is responsible for its propulsion?

Accepted Answer

The static friction force exerted by the road on the tires.

Question 5

A person pushes a crate across a rough surface. Which of the following is NOT an interaction in this scenario?

Accepted Answer

The magnetic force between the person and the crate.

Question 6

If a ball is dropped and falls toward the earth, what is the magnitude of the force the ball exerts on the earth?

Accepted Answer

It is equal in magnitude to the force the earth exerts on the ball, but opposite in direction.

Question 7

Two boxes, A and B, are pushed together on a frictionless table. Box B has a larger mass than box A. Which box experiences a greater acceleration?

Accepted Answer

Box A experiences a greater acceleration because it has less mass.

Question 8

In a system where a car is pulled by a truck with a rope, what is the acceleration constraint?

Accepted Answer

The car and the truck have equal accelerations: $$a_C = a_T$$

Question 9

A 200 kg crate is loaded into a 2000 kg truck. If the coefficient of static friction between the crate and the truck bed is 0.80, what is the maximum force that can be applied to the truck without the crate sliding?

Accepted Answer

The maximum force is $$F_{max} = \mu_s m_{crate} g = 0.80 	imes 200 	imes 9.8 = 1568\ 	ext{N}$$

Question 10

A safe hangs from a rope. What is the nature of the tension force in the rope?

Accepted Answer

The tension force pulls equally in both directions along the rope.

Question 11

Two boxes are connected by a massless string. If a force is applied to box B, what is the relationship between the tension forces at both ends of the string?

Accepted Answer

The tension is the same at both ends: $$T_{AS} = T_{BS}$$

Question 12

Blocks A and B are connected by massless string 2 and pulled across a frictionless table by massless string 1. B has a larger mass than A. How does the tension in string 2 compare to the tension in string 1?

Accepted Answer

The tension in string 2 is less than the tension in string 1.

Question 13

In a pulley system with two blocks connected by a string, which statement is correct regarding the tension in the string?

Accepted Answer

The tension is the same throughout the string if the string and pulley are massless and frictionless.

Question 14

A 1000 kg safe is lowered from a window using a rope over a pulley, attached to 500 kg of furniture. The coefficient of kinetic friction between the furniture and the floor is 0.50. What is the net force acting on the safe as it descends?

Accepted Answer

The net force is $$F_{net} = m$$_{safe}$$g - (m$$_{furniture}$$g \mu_k)$$

Question 15

Which step is NOT part of the problem-solving strategy for interacting-objects problems?

Accepted Answer

Ignore acceleration constraints between objects.

Question 16

If two objects move together, their accelerations are constrained to have the same magnitude. Which scenario best illustrates this?

Accepted Answer

A car is pulled behind a truck, both accelerating to the right: $$a_C = a_T$$

Question 17

Which of the following is a correct application of Newton's third law?

Accepted Answer

When you push against a wall, the wall pushes back on you with an equal and opposite force.

Question 18

In a system with two boxes connected by a string, which equation correctly represents the action/reaction pair between the boxes?

Accepted Answer

$$\vec{T}_{BA} = -\vec{T}_{AB}$$

Question 19

Which statement about forces in action/reaction pairs is correct?

Accepted Answer

The forces are equal in magnitude and opposite in direction, but act on different objects.

Newton’s Third Law and Interacting Objects: Systems, Forces, and Applications

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