1. Newton’s Laws of Motion
Linear Kinetics

2. Newton’s First Law of Motion
Law of Inertia
Every body will remain in a state of rest or constant motion (velocity) in a straight line unless acted on by an external force that changes that state
A body cannot be made to change its speed or direction unless acted upon by a force(s)
Difficult to prove on earth due to the presence of friction and air resistance

3. Newton’s Second Law of Motion
Law of Acceleration
A force (F) applied to a body causes an acceleration (a) of that body which has a magnitude proportional to the force, and takes place in the direction in which the force acts
Vitally important in sport as it forms the link between force and motion:
Force = mass × acceleration
F = m × a

4. Applications of Newton’s 2nd Law
Assuming mass remains constant, the greater the force the greater the acceleration
What is the acceleration of the ball (ball mass = 1.5 kg)?
F = 500 N
a = ?
F = m × a 
a = 333 m·s-2

5. Newton’s Third Law of Motion
Law of Reaction
For every force that is exerted by one body on a second body there is an equal (magnitude) and opposite (direction) simultaneous force exerted by the second body on the first
Therefore every force which is applied by a body is accompanied by a reaction force on that body
Difficult to visualise but can be felt:
e.g. In boxing the force applied by a punch is experienced by the opponent’s chin and the puncher’s hand

6. Examples of Newton’s 3rd Law
Ground Reaction Force (GRF) is a special type of force explained by Newton’s 3rd Law of Motion
Equal in magnitude and opposite in direction to the force applied to the ground by the body
Needs to be considered separately in horizontal (friction) and vertical (normal) directions

7. Summary Newton’s Law of Gravitation Newton’s First Law (Inertia)
Attractive forces exist between bodies (e.g. a body and the Earth) that are proportional to the product of their masses and inversely proportional to the distance between them
Newton’s First Law (Inertia)
A force is required to accelerate (i.e. change the velocity of) a body
Newton’s Second Law (Acceleration)
The acceleration of a body is proportional to the sum of the forces acting on it
Newton’s Third Law (Reaction)
Any body that applies a force to another body experiences a simultaneous reaction force that is equal in magnitude and opposite in direction to the applied force