Mechanics

SUVAT

SUVAT

Equations of motion that can be used when an object is moving at uniform acceleration

Distance

Scalar quantity that describes the amount of ground the object has covered

Displacement

Vector quantity that describes the overall distance travelled from the starting position

Speed

Scalar quantity that describes the distance travelled per unit time

Velocity

Vector quantity that describes the rate of change of displacement

Acceleration

Vector quantity that describes the rate of change of velocity

Uniform acceleration

Where the acceleration of an object is constant

Area under acceleration-time graph

Velocity

Gradient of velocity-time graph

Acceleration

Area of velocity-time graph

Displacement

Gradient of displacement-time graph

Velocity

Instantaneous velocity

The velocity of an object at a specific point in time

Resolving vectors

Splitting a vector into its vertical and horizontal components

Adding vectors using trig

Used when two vectors are perpendicular to each other. Use Pythagoras’ theorem to find the magnitude and trigonometry to find the direction

Adding vectors using a scale drawing

Used when vectors are at angles other than 90°. Use a ruler and protractor to find the magnitude and direction, making sure to note the scale used

Projectile motion

Vertical and horizontal components of a projectile’s motion are independent. Use SUVAT in two dimensions, ignoring air resistance so acceleration is constant

Free-body diagrams

A diagram which shows all the forces that act on an object

Newton’s first law

An object will remain at rest or travelling at a constant velocity, until it experiences a resultant force

Newton’s second law

The acceleration of an object is proportional to the resultant force experienced: F=ma

Newton’s third law

For each force experienced by an object, the object exerts an equal and opposite force

Terminal velocity

Frictional forces acting on an object are equal to the driving forces, so there’s no resultant force and no acceleration

Gravitational field strength

The force per unit mass exerted by a gravitational field on an object: g=F/m

Weight

The gravitational force that acts on an object due to its mass: W=mg

Momentum

The product of the mass and velocity of an object: p=mv

Principle of conservation of momentum

Momentum is always conserved in a closed system. Total momentum before = Total momentum after

Moments

The turning effect of a force. Force multiplied by the perpendicular distance from the line of action of the force to the point: Moment=Fx

Principle of moments

For an object in equilibrium, the sum of anticlockwise moments about a pivot is equal to the sum of clockwise moments

Centre of gravity

The point at which gravity appears to act

Uniform object

Centre of gravity is exactly at its centre

Work

The force causing a motion multiplied by the distance travelled in the direction of motion: W=FΔs

Kinetic energy

The energy an object has due to its motion

Gravitational potential energy

The energy an object has due to its position in a gravitational field

Principle of conservation of energy

Energy cannot be created or destroyed, only transferred from one form to another

Power

The rate of energy transfer

Efficiency

A measure of how efficiently a system transfers energy