1. Revision on Energy transformations Made by : Dr. Niveen Fawzy

2. Mechanical energy Energy: is ability to do work, or to make a change Work: is force applied on a body to displace it (move it) a distance in the direction of force Mechanical energy It’s energy of object due to it’s motion or position MECHANICAL ENERGY= POTENTIAL ENERGY + KINETIC ENERGY

7. The sum of potential & kinetic energies of an object under the effect of gravity is a constant value The conservation law of mechanical energy

8. Steps: -Push with your hand gently the pendulum & leave it Observation: It will move on both sides around its original position (A) -Maximum velocity is at point (A) Explanation: -Work is done to push the ball & stored as P.E at point (C ),When you leave it, P.E is gradually changed into K.E till reaching point (A) all M.E=K.E, then gradually velocity decreases till reaches maximum height velocity is zero at( C&B) = maximum P.E

9. How is a swing similar to a pendulum? -When swing is pushed,work done is stored in swing in form of P.E -While swing is moving, a gradual change occurs, as P.E is converted into K.E -When it passes by initial position, velocity is maximum, all M.E=K.E -When reaching maximum height, velocity is zero,& all M.E =P.E Conclusion: Object keeps its mechanical energy which alternates between potential & kinetic energies