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.
A 2 kg car moving with a speed of 2 m/sec starts up a hill. 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?
Solution Solving Problems Find beginning EK EK = ½ (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 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 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?