00:01
In this question, a boy and his key of mass 47 k's combined starts its motion from the top of a cliff, which is frictionless.
00:09
At the bottom of the cliff, the final velocity of the child is 3 .9 meter per second.
00:16
We have to find the height of the cliff.
00:20
As you can see that, the cliff is frictionless, that means there will be no loss of energy.
00:27
That means that the energy will be conserved.
00:32
So we will use conservation of energy to solve this question.
00:38
According to conservation of energy, change in kinetic energy is equal to negative of change in potential energy.
00:46
We can write final kinetic energy minus initial kinetic energy is equal to initial kinetic energy minus final kinetic energy.
00:56
So the initial kinetic energy is zero because initially the speed is also zero...