law of conservation ofEnergy

law of conservation Energy: this states that energy in in isolated system will stay constant.

mathematical representation of the law of conservation energy

Short version: Ei=Ef

long version: KEbefore + PEbefore = KEafter + PEafter 


Different types of Energy
Si units: In SI units, energy has units of Joules. 1 Joule = 1 kgms.
American Units are but not limited to: Foot-pounds, newtons, watts

7A.A ball with a mass of 2 kg is dropped from the top of the building that is 30 m high. what is the velocity of the ball when it is 10 m above the ground?  (20 m/s)

 use the conservation of Energy. the gravitational potential energy lost as the ball drops from 30 m to 10 m equals the kinetic energy gained

change in gravitational potential can be found using the difference in mgh.
mgh^f - mgh^i = 2kg * 10 m/s^2 * 10 m - 2kg * 10 m/s^2 *30 m = -400 joules

so 400 joules are converted from gravitational to kinetic energy, allowing us to solve for the velocity, v

400joules = 1/2 mv^2
400= v^2
v= 20 m/s                                                                                        A

7B. girl that is standing on 20 m house. she decides to jump off into the pool below. how fast is she moving when she hits the water?

   
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8A.  the total energy is distributed in kinetic, potential, thermal  but the leading energy when at rest is potential because the skater is not in motion.
8B. at the highest speed the energy thats leading is kinetic, because it is in motion.
8C.   in this photo the leading energy is potential because the skater is at the top of the ramp which means hes not speeding.
                                                                                                         C