# Standard EPS Shell Presentation 7.3 Conservation of Energy The idea that energy tranforms from one form into another without a change in the total amount is called the law of conservation of energy. The law of energy conservation says the total energy before the

change equals the total energy after it. 7.3 Conservation of Energy When you throw a ball in the air, the energy transforms from kinetic to

potential and then back to kinetic. Solving Problems A 2 kg car moving with a speed of 2 m/sec starts up a hill. How high does the car roll

before it stops? Solving Problems 1. Solution Find beginning EK EK = (2 kg) (2 m/s)2 = 4 Joules Assume energy before = energy after

EK = EP EP =mgh 4 J = mgh h = (4 Nm)/(2 kg)(9.8 N/kg) = .2 m A 3.0-kilogram toy dump truck moving with a speed of 2.0 m/s starts up a ramp. How high does the truck roll before it stops?

A 2.0-kilogram ball rolling along a flat surface starts up a hill. If the ball reaches a height of 0.63 meters, what was its initial speed? A 500.-kilogram roller coaster starts from rest at the top of an 80.0-meter hill. What is its speed

at the bottom of this hill? Find the potential energy of this roller coaster when it is halfway down the hill. A 2.0-kilogram ball is tossed straight up with a kinetic energy of 196 joules. How high does it go?

A 50.-kilogram rock rolls off the edge of a cliff. If it is traveling at a speed of 24.2 m/s when it hits the ground, what is the height of the cliff?