| Onsite |
D) Law of Conservation of Energy - unless work is done on or by a system, its total mechanical energy does not change.
1. Total Mechanical Energy
= PE + KE
Ex 1) Falling object(no friction)
Answer
As the Object Falls,
PE Lost = ....
...KE gained
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Predict how far up the incline each ball will go. (assume no friction)
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Why does each ball rise to the same height from which it began? |
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PE depends only on height. Ball stops when all KE turns into PE |
Energy changes
in a roller coaster
- Teachers Domain
Ex 2)
IF KE at A = 0
PE = mgh,
g = 10 m/s2
PE = 3 kg(10 m/s2)3 m
= 90 J
| PE | KE | |
| A | 90 J | 0 |
m = 3 kg h = 1 m
| B | PE | KE |
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30 J |
60 J |
m = 3 kg, h = 0
| C | PE | KE |
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0 J (h = 0) |
90 J |
m = 3 kg, h = 1 m
| D | PE | KE |
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30 J |
60 J |
m = 3 kg, h = 0
| E | PE | KE |
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0 J (h = 0) |
90 J |
m = 3 kg, h = 1 m
| F | PE | KE |
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30 J |
60 J |
m = 3 kg, h = 3 m
| G | PE | KE |
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90 J |
0 J |
| H | Never gets there! Doesn't have the energy to go any higher than G |
Physics of Designing Rollercoasters
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At what minimum height should you place the ball so it makes it all the way around the loop? |
UC Irvine
| LoopTheLoop.mov |LoopTheLoop.mpg |
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The ball has to be placed at a height above the top of the loop so it has the KE to continue. |
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