How do you calculate lost energy
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How do you calculate lost energy

[From: ] [author: ] [Date: 11-11-20] [Hit: ]
525 / 24.525 = .Total % Energy lost = (.Damn you air!......
A 100g ball is dropped from a height of 25m and reaches the ground with a speed of 10m/s. What fraction of the original energy is lost to air resistence? (The answer is 80% but how do calculate it?)

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Conservation of energy

Kinetic Energy + Potential Energy = Total Energy of the system

Since the ball is DROPPED, there is no Kinetic Energy at a height of 25m

therefore, the Total Energy of the system is just the Potential Energy at 25m = m*g*h =

(.1)(9.81)(25) = 24.525 J

This is the amount of energy that SHOULD BE at the bottom of the balls fall, but

Total Energy when the ball hits the ground is just Kinetic Energy = 1/2(m*v^2) =

1/2(.1)(100) = 5 J

The Total Energy lost is 24.525 - 5 = 19.525 J

19.525 / 24.525 = .796

Total % Energy lost = (.796)*(100) = 80%

Damn you air!

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PE = KE that is assuming no loss to air friction

So the actual KE / KE above equals the % KE remaining
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