H2 Physics - Motion & Forces

State the 4 main kinematics equations

• v = u + at

• s = ½(u + v)t

• s = ut + ½at²

• s = vt - ½at²

• v² = u² + 2as

State the 2 conditions for the 4 main kinematics equations to work.

• Motion of object is in a straight line.

• Acceleration of object is constant.

Define inertia of a body.

It is a body’s reluctance to start moving, or to change its motion once it has started.

Define mass.

It is the intrinsic property of a body which resists a change in motion (it is a measure of inertia of a body)

Define momentum.

It is the product of the mass and velocity of a body.

State Newton’s 1st Law

A body continues in its state of rest or uniform motion in a straight line, unless a resultant external force acts on it.

State Newton’s 2nd Law

The rate of change of momentum of a body is proportional to the resultant force acting on it and occurs in the direction of the force. (for SI units, k = 1)

State Newton’s 3rd Law

If a body A exerts a force on body B, then body B exerts an equal and opposite force on body A.

State the 2 formulae which arise from Newton’s 2nd Law (one for constant mass and one for constant mass flow)

• Constant mass: F = ma

• Constant mass flow: F = Δv(dm/dt)