Law of Conservation of Energy

Energy cannot be created nor destroyed

Law of Conservation of Energy

• Total energy before = total energy after

• KEi + PEi = KEf + PEf

8 m

5 kgExample #1

8 m

5 kg

Potential Energy (gravitational)

PE = m g h

PE = 196 J

PE = 98 J

PE = 0 J

PE = 294 J

PE = 392 J

Find the PE at each red dot

8 m

5 kg

PE = 196 J

PE = 98 J

PE = 0 J

PE = 294 J

PE = 392 J

Total Energy (PE+KE)

392 J

392 J

392 J

392 J

392 J

KE = 98 J

KE = 196 J

KE = 294 J

KE = 0 J

KE = 392 J

5 kg

8 m

PE = 392 J

KE = 0 J

What is the velocity of the rock at the bottom of the hill?

PE = 0 J

KE = 392 J

V = 2KE m

V = 2(392 J) 5 kg

v = 12.5 m/s

Example #2

Energy Song

Picture this a penny,Atop a hill and ready,It’s not moving it’s steady,Potential Energy.(Chorus)And now the penny’s rollingKinetic it’s a growingPotential it’s now loweringConserving Energy(Chorus)Falling, falling fasterIt is not hard to masterThe idea of this transfer toKinetic Energy(Chorus)

Reflect

• Write a statement that will help you to remember the relationship between Potential energy and Kinetic energy.

Rube Goldberg Energy Transfer

• http://www.youtube.com/watch?v=_ve4M4UsJQo

• http://www.youtube.com/watch?v=qybUFnY7Y8w