Newtonian Mechanics

Question 1

What is the definition of force
(including SI units)

Answer 1

Force = that which changes or tends to change the state of rest, or motion, of an object.
In the SI system, measured in Newtons (N)
A newton = the force that increases the velocity of one kilogram by one metre per second every second
(N=kg.m/s^2)

Question 2

What is Newton’s first law of motion?

Answer 2

In the absence of external forces, an object at rest remains at rest and an object in motion continues in motion with a constant velocity (at a constant speed in a straight line).

Therefore: if no force acts on an object the acceleration of the object is zero

Question 3

What is acceleration
(relationship to force and mass)

Answer 3

= the rate of change of velocity
The acceleration of an object is directly proportional to the force applied, and inversely proportional to its mass (Newton’s second law of motion)
f=ma

Question 4

Newtons second law of motion

Answer 4

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass

F=ma

Question 5

Newtons third law of motion

Answer 5

For every action there is an equal and opposite reaction.

Forces always occur in pairs. If object A exerts a force, F, on object B, then object B exerts an equal and opposite force, −F, on object A.