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on April 11, 2020
LAW OF CONSERVATION OF ENERGY GO BACK
The Law of Conservation of Energy states that Energy can neither be created nor destroy during transformation, it can only be converted from one form to another form.
A stone at height h possesses a potential energy of mgh. this potential energy is converted to kinetic energy when the stone is released.
Potential Energy + Kinetic Energy = constant
at the height h , v=0 then mgh= constant
when the stone is released and h=0,
= constant
Example
A stone of mass 3kg falls from height of 100m . What is the kinetic and potential energy at height 40m. What will be the velocity on reaching the ground ? take g=10
solution
At height 100m
PE + KE = constant
mgh + 0 =constant
3 x 10 x 100= constant
3000J = Constant
The potential energy at height 100m = 3000J
The kinetic Energy at height 100m=0
at height 40m
PE + KE = 3000
3 x 10 x 40 + KE= 3000
PE=1200J
KE=1800J
On reaching the ground
PE + KE= Constant
0 + KE = 3000
=3000
v= 44.72m/s
The total potential energy has been converted to kinetic energy on reaching the ground.
Energy Conversion in a Pendulum
When a pendulum oscillate from peak h to center c and back to peak h, potential energy is being converted to kinetic energy.
At peak h the total energy is constant PE + KE = Constant while KE=0
At Center c the PE=0 therefore KE=constant
At any point in between h and c , PE+KE =constant, loss in PE= Gain in KE
The velocity v of the pendulum at any point in between c and h can be calculated from above as
Posted in: Education
Topics:
law of conservation of energy
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