Forces 1

Motion sensor

A device that measures movement over time, often used in speed and acceleration experiments.

Distance–time graph

A graph showing how distance changes with time; gradient equals speed.

Flat line on distance–time graph

Object is stationary (no change in distance).

Straight diagonal line on distance–time graph

Object is moving at constant speed.

Curved line on distance–time graph

Object is accelerating or decelerating.

Speed equation

Speed = distance ÷ time.

Acceleration experiment

An experiment to investigate how velocity changes over time, often using a ramp, trolley, and light gates.

Light gate

Device that measures time taken for an object to pass through, used to calculate velocity or acceleration.

Acceleration

Change in velocity per unit time; measured in m/s².

Acceleration equation

a = (v - u) ÷ t.

v (final velocity)

The speed at the end of motion.

u (initial velocity)

The speed at the start of motion.

t (time)

Duration over which the change in motion occurs.

Acceleration results

Show how velocity changes over time; can be used to calculate average acceleration.

Velocity–time graph

A graph showing how velocity changes with time; gradient = acceleration, area under = distance.

Flat line on velocity–time graph

Object moving at constant velocity.

Upward sloping line on v–t graph

Object accelerating at constant rate.

Downward sloping line on v–t graph

Object decelerating at constant rate.

Area under velocity–time graph

Represents distance travelled.

Gradient of velocity–time graph

Equals acceleration.

F = ma

Force equals mass times acceleration (Newton's Second Law).

F (force)

Measured in newtons (N); a push or pull acting on an object.

m (mass)

Measured in kilograms (kg); the amount of matter in an object.

a (acceleration)

Rate of change of velocity; measured in m/s².

Newton’s First Law

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

Newton’s Second Law

F = ma; the acceleration of an object is proportional to the force applied.

Newton’s Third Law

For every action, there is an equal and opposite reaction.

Terminal velocity

The constant speed reached when air resistance balances weight; no more acceleration.

Skydiver example

Accelerates at first, then reaches terminal velocity when air resistance = weight.

Resultant force

The overall force acting on an object; needed to change motion.