Mechanics definitions: CAIE Physics A-level

Common definitions one needs to know for Mechanics

Define Force

The rate of change of momentum

Define the moment of a force

force x perpendicular distance (of line of action of force to the point)

State the principle of conservation of momentum

total momentum before (a collision) = total momentum after if no resultant external force/ for an isolated system

Define momentum

The mass of a body times its velocity

Define velocity

Change in displacement / time taken.

Define the centre of gravity

The point at which the whole weight of the body is taken to act

Define the centre of mass

The point at which the whole mass of the body maybe considered to act

Define work done

The force multiplied by the displacement in the direction of the force.

Define power

Work done per unit time.

State what is meant by the mass of a body

Mass is the quantity of matter

State Newton’s 2nd Law

(resultant) force proportional to rate of change of momentum

State the principle of moments. [2 marks]

Sum of CW moments = Sum of ACW moments

about the same point for (an object in rotational) equilibrium.