MOTION, FORCES & ENERGY

What is speed?

Distance travelled per unit time (scalar quantity

What is velocity?

Speed in a given direction (vector quantity)

What is acceleration?

Rate of change of velocity per unit time

Speed formula

speed = distance ÷ time

Acceleration formula

acceleration = change in velocity ÷ time

What is a scalar quantity?

A quantity with magnitude only (e.g. speed

What is a vector quantity?

A quantity with magnitude and direction (e.g. force

What does a distance-time graph show?

How distance changes over time

What does gradient of distance-time graph represent?

Speed

What does a speed-time graph show?

Speed changes over time

What does gradient of speed-time graph represent?

Acceleration

What does area under speed-time graph represent?

Distance travelled

Newton’s First Law

An object stays at rest or constant velocity unless acted on by a resultant force

Newton’s Second Law

Force = mass × acceleration

Newton’s Third Law

Every action has an equal and opposite reaction

Force equation

F = ma

Weight equation

weight = mass × gravitational field strength (W = mg)

What is momentum?

Product of mass and velocity

Momentum equation

momentum = mass × velocity

Conservation of momentum

Total momentum before = total momentum after in a closed system

What is work done?

Energy transferred when a force moves an object

Work done equation

work done = force × distance moved in direction of force

Power definition

Rate of energy transfer

Power equation

power = work done ÷ time

Kinetic energy definition

Energy due to motion

KE equation

KE = ½mv²

Gravitational potential energy definition

Energy due to height

GPE equation

GPE = mgh

What is efficiency?

Ratio of useful output energy to total input energy × 100%