What is energy?
The ability to do work or cause change.
An 25kg object is sitting on the top of a 30m cliff on mars which has a gravity of .5. What is the object's total potential energy?
Gpe=mgh = 25*30*.5 = 375J
An 10 kg object is moving down a hill. At the bottom of the hill it has a velocity of 5m/s. What is the object's total kinetic energy?
ke=1/2*m*V*V = 5*5*5=125J
A 100kg person dives from an airplane traveling 3*10^3m above the ground. After 5 seconds, he is traveling at a velocity of 49 m/s. Calculate his mechanical energy in terms of both kinetic and potential. Ignore friction
Total energy: 2.94*10^6j=mgh
2.94*10^6-1.2*10^5=2.82*10^6j of GPE remaining
Ke =1.2*10^5 j
A person is bobsledding down a hill. At the bottom of the hill, the sled moves with a velocity of 50m/s. If the man and sled had a combined mass of 250kg, how tall was the hill?
KE = 250*.5*50^2 = 312500 j
GPE = 250 * 9.8 * h = 312500
h=127.5m
GPE = 70*9.8*100 = 68600 j
68600 = .5*70*V^2
V*V = 1960j
V=44.3m/s