SACE Stage 2 Physics — Motion 1.2

Impulse & Δp

A ball bounces elastically off a wall. Watch how the change in momentum is always perpendicular to the wall, regardless of the angle of incidence.

Δp triangle

Mass

× 10 kg

Speed

× 10 m s⁻¹

Angles

Impulse calculation

Magnitudes

Key idea

Only the component of momentum perpendicular to the wall changes. The parallel component is unchanged. So Δp always points directly away from (or into) the wall, no matter the angle of approach.