Energy Kinetic and Potential

What is Energy? The ability to do work. Work = Force X Distance Forms of Energy: ElectricalMechanical ThermalRadiant GravitationalNuclear

The total amount of energy in a closed system is conserved. That is to say that energy can not be created nor destroyed, but can transform from one type of energy into another. Examples: rock falling down a hillside solar energy changing to electrical energy chemical energy changing to radiant energy nuclear energy changing to thermal energy

Energy given to an object due to its position above the earth’s surface. Potential Energy = Mass X Gravity X Height Kinetic Energy = ½ mass X Velocity 2 Energy is measured in Joules!

Gravitational Potential Energy = Mass ( Kg) X Gravity (9.8 m/s/s) X Height ( M ) How much potential energy would a 3 Kg rock have if it is placed on a hill that is 20 meters tall? M = 3 KgG = 9.8 m/s/s H = 20 meters PE = 3 Kg X 9.8m/s/s x 20 m = 588 Joules =.588 Kjoules

Kinetic Energy = ½ Mass ( Kg) X Velocity 2 (m/sec) A 30 Kg athlete is running with a velocity of 18 m/sec toward the finish line, what is her kinetic energy? M = 30 KgV = 18 m/sec KE = ½ 30 Kg x (18 m/sec) 2 KE = 4860 Joules

Conservation of Potential Energy Since energy can not be created nor destroyed, an object with gravitational potential energy will transform that energy into kinetic energy as it descends. Since energy can not be created nor destroyed, an object with gravitational potential energy will transform that energy into kinetic energy as it descends.

Pendulum, Pendulum, device consisting of an object suspended from a fixed point that swings back and forth under the influence of gravity High Kinetic Zero Potential High Potential Zero Kinetic High Potential Zero Kinetic

A high diver in the circus, or a platform diver in the Olympics are great examples of the Law of Conservation of Energy. Imagine a 60 Kg diver at the top of a platform that is 20 meters above the pool. What are the potential and kinetic energies at 20 m, 15m, 10 m and 2 m above the pool? 20 M 15M 10M 2M

Complete the following table Height above the ground (m) Potential Energy (Joules) Kinetic Energy (Joules) 30 4,312 0 A 30 Kg rock is dropped from a 30 meter tall cliff.

High jumpers are also great examples of the law of conservation of energy. The jumper starts with zero potential energy on the ground, but creates great kinetic energy by running toward the high jump bar.

The jumper then creates vertical lift and changes their kinetic energy into potential energy as she rises toward the peak of her jump. KE i + PE i = KE f + PE f

Neglecting air resistance, a high jumper could use their top sprinting speed to determine how high they could jump. If a 60 Kg athlete can run 8 m/sec, how high could they possibly jump off of the ground? M = 60 KgV = 8 m/sec PE i = 0 JoulesKE f = 0 joules So:KE i = Pe f Therefore:½ (60Kg) X (8m/sec) 2 = 60Kg x 9.8 m/s/s x H H = ½ (60 Kg) X (8 m/sec) 2 / 60 Kg x 9.8 m/s/s = 3.3 m

Pole Vaulting Also an example of the law of conservation of energy Also an example of the law of conservation of energy The pole is used as a means to transfer energy from the athlete, to the pole and finally back to the athlete The pole is used as a means to transfer energy from the athlete, to the pole and finally back to the athlete The composition of the pole gives definite advantage to the athlete The composition of the pole gives definite advantage to the athlete

kinetic Potential stored Kinetic Potential

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Roller coasters and many other amusement park rides are excellent examples of physics principles. In a 5 paragraph, typed essay describe the physics involved with a specific amusement park ride of your choice. Be sure to underline specific physics terms and references to physics principles or laws within your writing. Double space and use size 12 font. A full page labeled diagram should be included. Use your knowledge of Newton’s laws of motion, gravitational force, centripetal force and acceleration, kinetic and potential energies.