Physics A level mechanics 2

Centre of Mass

The average point of all parts of an object weighted according to their mass, through which the total mass is said to act.

Conservation of Energy

In a closed system with no external forces, the energy before an event is equal to the energy after the event.

Conservation of Momentum

In a closed system with no external forces, the momentum before an event is equal to the momentum after the event.

Drag

The resistance against the motion of an object through a fluid, usually proportional to the speed of the object.

Efficiency

The useful output of a system divided by the total output.

Elastic Collision

A collision where the kinetic energy before an event is equal to the kinetic energy after the event.

Equilibrium

An object is in equilibrium when the moments about a point are balanced and the resultant force is zero.

Force

The rate of change of momentum of an object; the product of mass and acceleration.

Friction

Resistance against motion caused by air or surface contact.

Gravitational Potential Energy

The energy gained by an object when it is raised in a gravitational field.

Impulse

The change of momentum of an object when a force acts on it, equal to the area underneath a force-time graph.

Inelastic Collision

A collision where the kinetic energy before an event is not equal to the kinetic energy after the event.

Kinetic Energy

The energy an object has due to its motion.

Lift

A force acting perpendicular to the flow of air or liquid around an object, typically upward against gravity.

Moment

The product of a force and the perpendicular distance from the line of action to the pivot.

Momentum

The product of an object’s mass and its velocity.

Newton’s First Law

An object at constant velocity remains at that velocity unless acted on by a resultant force.

Newton’s Second Law

An object acted upon by a resultant force will accelerate, with acceleration inversely proportional to mass.

Newton’s Third Law

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

Power

The work done by a system divided by the time taken.

Resultant Force

The sum of all forces acting on an object.

Scalar

A quantity with only magnitude and no direction.

Terminal Velocity

The maximum velocity an object can achieve, where frictional and driving forces are balanced.

Vector

A quantity with both magnitude and direction.

Weight

The force of gravity on an object, the product of mass and acceleration due to gravity.

Work Done

A force applied over a distance; the energy transferred in that distance.