Newton's Laws of Motion

Question 1

What is the simplest intuitive definition of a force?

Accepted Answer

A push or a pull.

Question 2

Why is force mathematically categorized as a vector quantity?

Accepted Answer

It has both magnitude and direction.

Question 3

What is the primary purpose of a free-body diagram (FBD)?

Accepted Answer

To illustrate all external forces acting on a body.

Question 4

Which category of forces is the only one that affects a system's motion?

Accepted Answer

External forces.

Question 5

According to Newton's first law, what is required to change an object's velocity?

Accepted Answer

A net external force.

Question 6

What is the term for a body's tendency to remain at rest or in motion at a constant velocity?

Accepted Answer

Inertia.

Question 7

Which physical quantity serves as the standard measure of an object's inertia?

Accepted Answer

Mass.

Question 8

How does the mass of an object on Earth compare to its mass on the Moon?

Accepted Answer

They are identical (mass is constant).

Question 9

How is acceleration mathematically related to the net external force?

Accepted Answer

Directly proportional ($a \propto F_{net}$).

Question 10

What happens to a system's acceleration if its mass is doubled while the net force remains constant?

Accepted Answer

Acceleration is halved.

Question 11

State the standard equation for Newton's second law of motion.

Accepted Answer

$$F_{net} = ma$$

Question 12

Define the SI unit of force (Newton) in terms of base units.

Accepted Answer

$$1\text{ N} = 1\text{ kg} \cdot \text{m/s}^2$$

Question 13

What is the formula used to calculate the magnitude of an object's weight?

Accepted Answer

$$w = mg$$

Question 14

Why does the weight of an object vary depending on its location in the universe?

Accepted Answer

Acceleration due to gravity ($g$) changes.

Question 15

What condition must be met for an object to be considered in "free-fall"?

Accepted Answer

Gravity is the only force acting on it.

Question 16

State Newton's third law of motion regarding interacting bodies.

Accepted Answer

Forces are equal in magnitude and opposite in direction.

Question 17

Why do the two forces in an action-reaction pair NOT cancel each other out?

Accepted Answer

They act on different systems (objects).

Question 18

In the context of Newton's third law, what is "thrust"?

Accepted Answer

A reaction force that pushes an object forward.

Question 19

When a person walks, what specific force provides the forward acceleration?

Accepted Answer

The floor pushing forward on the feet.

Question 20

What is the general definition of friction?

Accepted Answer

A force opposing relative motion between contact surfaces.

Question 21

In which direction does friction always act relative to the contact surface?

Accepted Answer

Parallel to the surface.

Question 22

Compare the typical magnitudes of static friction and kinetic friction.

Accepted Answer

Static friction is usually greater.

Question 23

What is the formula for the magnitude of kinetic friction ($f_k$)?

Accepted Answer

$$f_k = \mu_k N$$

Question 24

In friction equations, what does the symbol $N$ represent?

Accepted Answer

Normal force (perpendicular to the surface).

Question 25

What are the units for the coefficient of friction ($\mu$)?

Accepted Answer

It is unitless (dimensionless).