Mechanical Energy Gravitational Potential Kinetic Energy Gravitational Potential

Mechanical Energy Gravitational Potential & Kinetic Energy

Gravitational Potential Energy: Note: n Stored energy of a raised object Gravitational Potential Energy (J) Mass of object (kg) Gravity (N/kg) Same formula as W = Fd

How much potential energy does a 61. 2 kg boy have if he is sitting on his bed, 0. 5 m above the floor? m = 61. 2 kg g = 9. 8 N/kg ∆h = 0. 5 m

A 0. 04 kg rubber ball drops from a height of 5 m to the ground & bounces back to a height of 3 m. a) How much potential energy does the ball lose on the trip down? m = 0. 04 kg g = 9. 8 N/kg ∆h = 5 m b) How much potential energy does the ball regain on the trip back up?

Kinetic Energy: Energy of an object due to its motion n Result of work having been done to the object n Kinetic Energy (J) Mass of object (kg) Speed of the object (m/s)

What is the kinetic energy of a 6 kg curling stone sliding at 4 m/s? m = 6 kg v = 4 m/s

What is the speed of a 5. 44 kg shotput if its kinetic energy is 68 J? m = 5. 44 kg Ek = 68 J

A 0. 5 kg rubber ball is thrown into the air. At a height of 20 m above the ground, it is traveling at 15 m/s. What is the ball’s Ek & Eg? m = 0. 5 kg v = 15 m/s So ball has m = 0. 5 kg 154. 25 J of g = 9. 8 N/kg total energy h = 20 m

BUT…. total energy (ET) still the same throughout Eg = high Ek = zero Eg = high Ek = low Eg = lower Ek = higher Eg = higher Ek = lower Eg = zero Ek = high

Total Mechanical Energy (ET): n Energy can be transferred or transformed, never lost Law of Conservation of Energy *If friction negligible n. If friction is not negligible then….