Why not Does energy just disappear No Law of Conservation of Energy energy cannot be created nor destroyed energy can change forms 1 st Law of Thermodynamics energy can do work or produce heat but it is always conserved ID: 784007
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Slide1
Conservation of Energy
Was the potential energy and kinetic energy from the lab yesterday the same value?
Why not?
Slide2Does energy just disappear? No!
Law of Conservation of Energy
: energy cannot be created nor destroyed.
-energy can change forms
1
st
Law of Thermodynamics
: energy can do work, or produce heat, but it is always conserved.
How can we make things more efficient?
Slide3Work
Work = force x distance
(J) (N) (m)
Work is zero when an object is not moving.
Slide4Practice Problems
A crane uses an average force of 5,200N to lift a girder 25m. How much work does a crane do?
An apple weighing 1N does 1J of work. How far did it fall?
Slide5A bicycle’s brakes apply 125N of frictional force to the wheels as a bike moves. If the bike does 1,750 J of work, how far did it move?
A mechanic uses a hydraulic lift to raise a car weighing 11,760N 0.50m off the ground. How much work does the lift do on the car?