Chapter 8 - Newton's Laws of Motion

Question 1

What is Newton’s first law of motion?

Answer 1

An object remains at rest or in uniform motion unless acted on by a force.

Question 2

What is Newton’s second law of motion?

Answer 2

F = ma

Question 3

What is the equation for weight of an object when the force of gravity is the only force acting on the object?

Answer 3

W = mg

Question 4

What is mass?

What is inertia?

Answer 4

The mass of an object is a measure of its inertia.

Inertia is an object’s resistance to change of motion.

Question 5

Terminal velocity (a = 0) occurs when…

Answer 5

…the drag force on an object is equal and opposite to its weight (vertical motion) or motive/driving force (horizontal motion).

Question 6

Stopping distance =

Answer 6

Stopping distance = Thinking distance + Braking distance

Question 7

What is the aim of car safety features?

Answer 7

To increase impact time thus reducing impact force.

Question 8

When an object of mass m is acted on by two unequal forces F1 and F2 acting in opposite directions and F1 > F2…

Answer 8

Resultant force = F1 - F2 = ma

Lift example:
Resultant force, F = T - mg
(i.e. T - mg = ma)

Car and trailer example:
Assume air resistance is negligible.
Resultant force of car = F - t
(i.e. F - t = ma)
Resultant force on trailer = T
(i.e. T = ma)

Question 9

What is friction?

Answer 9

The force that opposes the motion of a surface that moves or tries to move across another surface.

Friction is independent to the horizontal component of speed.

Question 10

What is drag?

Answer 10

Drag (air resistance) is the force of resistance on the motion of an object in a fluid.

Drag increases with speed and cross-sectional area of an object.

Question 11

What is terminal velocity?

Answer 11

The constant velocity reached by an object when the frictional or drag force is equal and opposite to the weight of the object (vertical motion) or driving/motive force (horizontal motion).

Question 12

What effect does viscosity have on drag force?

Answer 12

A more viscous liquid exerts a greater drag force on a moving object.

A greater drag force will cause a falling object to reach terminal velocity faster.

Question 13

What is Newton’s Third Law?

Answer 13

If an object A exerts a force on object B, then object B exerts an equal but opposite force on object A.

Question 14

What is lift?

Answer 14

An upward force on an object moving through a fluid.