IGCSE PE: Principles of force

Force

A push or a pulling action applied upon an object (measured in Newtons, or N for short)

Newton's First Law of Motion

An object in motion stays in motion at the same speed and in the same direction, and an object at rest stays at rest unless acted upon by an external force

Newton's Second Law of Motion

An object will accelerate when acted upon by an external force. The acceleration of the object is proportional to this force and is in the direction by which the force acts

A force can cause a moving object to decelerate

As players reach the ball, they need to slow down. They will apply force to the ground in the opposite direction to the one they are running in. This will cause them to decelerate

Isaac Newton

English scientist who discovered the laws that govern motion and gravity

Newton's Third Law of Motion

For every action there exists an equal and opposite reaction

Newton's Force equation

Force (N) = mass (in kg) x acceleration (a) Or F = ma

Mass

The quantity of matter in a body regardless of its volume or of any forces acting on it (measured in kilograms or kg)

A force can cause an object/body at rest to move

The racquet will remain at rest until the player applies a force to move it backwards to cause a backswing to prepare to hit the ball.

Acceleration

The rate at which an object changes speed (measured in metres per second, or m/s2)

Inertia

The resistance of an object to any change in its state of motion

A force can cause a moving object/body to accelerate

When squash players need to increase their speed to run across the court, they will apply a greater force against the ground. This causes them to accelerate in the desired direction to reach the ball.

A force can cause a moving object or body to change direction

When the ball comes back from the wall, the squash player's racquet will hit the ball and exert a force to change the direction the ball will travel in. The ball will now travel back towards the wall.

A force can cause an object/body to change its shape

When the ball hits the wall/racquet, it will deform as it transfers momentum from one direction and transfers it to the new direction it is forced to travel in.

Acceleration can be either a positive or negative number

positive number = getting faster = shuttlecock when hit negative number = getting slower = air resistance and gravity slow it down