Work, Energy and Momentum

Work, Energy and Momentum

1. GRAVITATIONAL POTENTIAL ENERGY

   • Gravitational Potential Energy is energy stored in an object because of its position in the Earth's gravitational field.
     • When an object is moved up, its gravitational potential energy increased, this increase of GPE is equal to the work done on it by the lifting force.
     • When an object moves down, its Gravitational Potential Energy decreases. This decrease of GPE is equal to the work done by the force of gravity acting on it.
   • The work done when an object moves up or down depends on 1) How far it is moved vertically (change in height) and 2) Its weight
   • Change in Gravitational Potential Energy (joules) = its weight (newtons) x its change of height (metres)
     • Change in GPE (J) = mass (kg) x gravitational field strength (N/kg) x change of height (metres)
   • Ep = m x g x h

2. ENERGY and WORK

   • When a FORCE moves an OBJECT through a DISTANCE, ENERGY IS TRANSFERRED and WORK IS DONE.
     • so,, energy transferred = work done
   • Work done = force applied x distance moved in the direction of the force
     • W (joules, J) = F (newtons, N) x D (metres, m)
   • FRICTION at WORK
     • Work done to overcome friction is transferred as energy that heats the objects that rub together and the surroundings