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Explore how energy transforms at various points with examples like roller coasters losing energy through sound, friction, and air resistance. Learn about machines' efficiency and the law of conservation of energy. Discover equations and sample problems for assessing energy transformations and efficiency.
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Section 4 Conservation of Energy
I. Energy Transformations At the top of the hill, PE is at it’s maximum. What about KE? KE = 0.0 J PE = mgh PE = (515 kg)(9.8 m/s2)(70.0 m) PE = 353,290 J
I. Energy Transformations At the bottom of the hill, KE is at it’s maximum. What about PE? PE = 0.0 J KE = ½mv2 KE = ½(515 kg)(37.1)2 All of the PE was converted to KE. KE = 353,290 J
As the car reaches the top of the 2nd hill, KE = PE. KE = ½mv2 KE = ½(515 kg)(26.2)2 PE = mgh PE = (515 kg)(9.8 m/s2)(35.0 m) KE = 176,758 J PE = 176,645 J
II. The Law of Conservation of Energy Energy cannot be created or destroyed. 1. Energy changes from one form to another Roller coasters lose energy through: Sound Friction Air Resistance
III. Efficiency of Machines Not all work done by a machine is useful 1. Work Input is not equal to Work Output Energy is lost through: Sound Friction Air Resistance
Example: With this pulley system, we should be able to lift 100 pounds with only 25 pounds of force. However, friction and heat would cause some of the input force (25 lbs.) to be lost.
Sample problems pg. 407 Questions 1 – 3