Potential Energy Stored energy or energy due to

Potential Energy Stored energy or energy due to position/location

There are 2 types of potential energy… • 1. gravitational potential depends on height of object from the zero level • 2. elastic potential depends on the stretch or compression of a spring or elastic material

PEg=mgh • m is mass in kg • g is gravitational acceleration • h is height above zero level in meters

Example 1: • A 70. 0 kg stuntman attached to a bungee cord jumps off a bridge that is 50 m above a river. If the cord stops 6 m above the surface of the water, calculate the potential energy of the stuntman just before he is pulled back by the bungee cord.

PEe=1/2 kx 2 • k is “spring constant” which will be a given 90% of the time • x is the difference between stretched and un-stretched length of the spring or string

Example 2: • If the stuntman form example 1 used a bungee cord with an un-stretched length of 15 m and a spring constant of 71. 8 N/m, what is the potential elastic of the bungee cord?

Conservation of Energy • Energy will change from potential to kinetic and back without loss or gain during a “story” or situation.

Example 3: • A 150 lb woman hangs out the window of a burning building. If the window is 25 m above the surface of the firemen’s net, what is her potential energy? • As she falls, her PE transfers into KE. If all of her PE is converted over, how long will it take her to reach the waiting firemen?

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