Conservation
of Energy
As a reminder; the conservation of energy states that the total amount of energy in a system is constant over time (i.e. if you put 5J in you get 5J out). A consequence of this is that energy can neither be created nor be destroyed; and can only be transformed from one state to another.
As a reminder; the conservation of energy states that the total amount of energy in a system is constant over time (i.e. if you put 5J in you get 5J out). A consequence of this is that energy can neither be created nor be destroyed; and can only be transformed from one state to another.
We
can write the principle of conservation of energy as a formula:
Calculation
The
Diagram below shows a man at the top of a building, calculate how much energy
he has at the start and hence show how much energy he has at the end.
Energy at
the top
GPE = mgh
GPE = 50 x 10 x 20
GPE = 10,000J
GPE = 50 x 10 x 20
GPE = 10,000J
KE = 0J
(He isn’t currently moving)
Total
Energy = KE + GPE
Total Energy = 0 + 10,000
Total Energy at start = 10,000J
Total Energy = 0 + 10,000
Total Energy at start = 10,000J
Energy at
the bottom
GPE = 0J
Total
energy Start = Total energy End
Total
energy end = KE + GPE
10,000J = KE + 0J
10,000J = KE + 0J
KE = 10,000J
KE = ½ mv2
10,000 = ½ x 50 x v2
v = 20m/s
10,000 = ½ x 50 x v2
v = 20m/s
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