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LearnEdexcelYPH112018 specificationWPH14 · Unit 4: Further Mechanics, Fields and ParticlesFurther mechanics

WPH14 · Module

Further mechanics

3 subtopics≈ 110 min in total

Start the module: Kinematics of circular motion Open graphing calculator

Kinematics of circular motion
Angles in circular motion are measured in radians: $\theta=\dfrac sr$ , so a full turn is $2\pi$ rad. Angular speed $\omega$ is the rate of change of angle, $\omega=\dfrac{2\pi}T=2\pi f$ . A point at radius $r$ moves with linear speed $v=r\omega$ . Every point on a rigid rotating object has the same $\omega$ , but points further out move faster.
≈ 30 min
Conservation of momentum and collisions
In any interaction with no external resultant force, total momentum is conserved, in every direction. In an elastic collision kinetic energy is also conserved, and the relative speed of approach equals the relative speed of separation. In an inelastic collision some kinetic energy becomes heat, sound or deformation. In two dimensions, conserve momentum separately in perpendicular directions.
≈ 40 min
Centripetal acceleration and force
An object moving in a circle accelerates towards the centre: $a=\dfrac{v^2}r=r\omega^2$ . This needs a resultant force towards the centre, $F=\dfrac{mv^2}r=mr\omega^2$ , called the centripetal force. It isn't a new kind of force: tension, gravity, friction or a normal reaction provides it. Being perpendicular to the velocity, it changes direction but does no work.
≈ 40 min