Question

State the law of conservation of energy. Give an example,
​

Answer 1

the energy in universe is constant and it neither be created nor destroyed

Answer 2

$\bold{Law\: of\: conservation\: of\: energy -:}$ 

Law of conservation of energy states that Energy is neither be created or nor destroyed. Energy can be changed only from one form to another. in other words we can say " the total energy of a closed system always remains constant".

This law is valid in all situation and for all type of transformations.

Let's consider an example.

an object of mass, "m" be managed to fall freely from a height, "h".

at the begin, potential energy is "mgh" but kinetic energy is zero.

$\bold{Why\: the\: kinetic\: energy\: zero }$ ?

It is zero because its velocity is zero. therefore, the total energy of the object is "mgh". since it falls, its potential energy will change to kinetic energy. if "v" is the velocity of the object at a provided instant,  the kinetic energy would be 1/2m². Since the fall of object continues, would decrease potential energy whereas the kinetic energy would increase. when the object is about to come the ground the ground, then "h" = 0 and "v" will be the greatest. so, the kinetic energy will be the largest and potential energy the smallest. 

However, the sum of the potential and kinetic energy would be similar at all points.
$<b>$
Kinetic energy + potential energy = constant.