Rotational Momentum & Power

Angular Momentum

Angular Momentum, (L): momentum = mass x velocity.

Angular momentum occurs in rotational movement

L (kgm2s-1) = Iω

angular momentum before = angular momentum after

Conservation of angular momentum

Most children and adults have tried to swivel themselves on a chair without touching the floor and the discussion starts with this challenge. Presenter Dr Yan Wong then demonstrates that by holding onto a spinning bicycle wheel, circular motion can be initiated and reversed.

Impulse

Impulse: change in momentum

Angular Impulse, ΔL: change in angular momentum

ΔL = TΔt

(small torque for long duration = large torque for small duration)

Work & Power

Work done = force x perpendicular distance… so…

Work done = torque x angle rotated W = Tθ

Power = force x speed… so…

Power = torque x angular velocity P = Tω