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Potential Energy. Energy due to an objects position Can either be due to: Elasticity Gravity Gravitational Potential Energy (GPE) Depends on height and mass GPE = height X gravitational acceleration X mass Units: Joules. I. Potential Energy. http://www.youtube.com/watch?v=qJEopoD-YYI
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Energy due to an objects position • Can either be due to: • Elasticity • Gravity • Gravitational Potential Energy (GPE) • Depends on height and mass • GPE = height X gravitational acceleration X mass • Units: • Joules I. Potential Energy
http://www.youtube.com/watch?v=qJEopoD-YYI • A 65 kg rock climber ascends a cliff. What is the climber’s gravitational potential energy at a point 35 m above the base of the cliff? • Identify the known and unknown variables • Known: height is 35m & mass is 65kg • Unknown: GPE • Write out equation for GPE • Plug in numbers and determine answer. • GPE = 35m X 9.8m/s2 X 65 kg • Answer = 22,295 Joules Math Skills – GPE #1
In Harry Potter and the Sorcerer’s Stone by J.K. Rowling, Ron Weasley manages to knock a troll out by levitating its club and then dropping the club on the troll’s head. http://www.youtube.com/watch?v=QJtyZ3aT5fY&feature=related • If the troll is 4 meters tall and Ron manages to drop the club, weighing 50 kg, from 3 meters above the troll’s head, how much potential energy will the club have before it is dropped? • Identify the known and unknown variables • Known: height is 7 m & mass is 50kg • Unknown: GPE • Write out equation for GPE • Plug in numbers and determine answer. • GPE = 7 m X 9.8m/s2 X 50 kg • Answer = 3430 Joules Math Skills – GPE #2
http://www.youtube.com/watch?v=v3mP-EVNVLA&feature=related • At Cambridge University, a piano is dropped off of a dorm to symbolize the last day you are able to drop a class. • What is the potential energy of the piano (mass of 317 kg) if they push it off the 5th story (a height of 20 meters)? • Identify the known and unknown variables • Known: height is 20 m & mass is 317 kg • Unknown: GPE • Write out equation for GPE • Plug in numbers and determine answer. • GPE = 20m X 9.8m/s2 X 317 kg • Answer = 60,172 Joules Math Skills – GPE #3