Physics Lecture W & E 3: Potential Energy & Tmc
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PHYSICS LECTURE W & E – 3: POTENTIAL ENERGY & TMC
POTENTIAL ENERGY . Stored Energy . Associated with an object that has the potential to move because of its position relative to some other location . ______. SI unit for potential energy is a Joule (J) which is equivalent to newtons times meters (N·m).
GRAVITATIONAL POTENTIAL ENERGY . The energy associated with an object due the object’s position relative to some gravitational source . Depends on both the height and the free-fall acceleration . It must be measured relative to some zero level. . FORMULA: gravitational potential energy = mass x free-fall acceleration x height
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ELASTIC POTENTIAL ENERGY . The energy stored in any stretched or compressed object . Depends on the distance the object is compressed or stretched from its relaxed length . The spring constant (k) is a measure of a spring’s resistance to being compressed or stretched. o ______o ______o ______. FORMULA: o elastic potential energy = ½ x spring constant x (distance compressed or stretch)2
o ______
POTENTIAL ENERGY EXAMPLE PROBLEM: A 70.0 kg stuntman is attached to a bungee cord with an unstretched length of 15.0 m. He jumps off a bridge spanning a river from a height of 50.0 m. When he finally stops, the cord has a stretched length of 44.0 m. Assuming the spring constant of the bungee cord is 71.8 N/m, what is the total potential energy relative to the water when the man stops falling? G:
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1 PHYSICS LECTURE W & E – 3: POTENTIAL ENERGY & TMC
CONSERVATION OF MECHANICAL ENERGY
. Mechanical energy is the sum of kinetic energy and all forms of potential energy
o ______
. In the absence of friction, Mechanical Energy is conserved.
o ______
o ______
. Conservation of Mechanical Energy Principle o Initial mechanical energy = final mechanical energy (in the absence of friction)
o ______
o ______
CONSERVATION OF MECHANICAL ENERGY EXAMPLE PROBLEM:
Starting from rest, a child with a mass of 25.0 kg zooms down a frictionless slide from an initial height of 3.00 m. What is her speed at the bottom of the slide?
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