Originally Posted by **RishabhChhajer** we know that energy=work done=F*s
f=ma
therefore, e=ma*s
if initial velocity is 0,acceleration is final velocity divided by the time taken
therefore,e=m*v/t*s
velocity is distance pet unit time
therefore,e=m*(s*s/t*t)
e=m*(s^2/t^2)
e=m*v^2
how is this possible when we know that kinetic energy of a body is
1/2mv^2 ?? |

The work done by a force exerted by, say, your hand, doesn't always change the speed and thus the kinetic energy. For example, let's say that you're moving a book across a table by pushing it from point A to point B where the speed is constant and in a straight line, i.e. force is in direction of motion. Then the work done by

*you* is Force x distance. The energy that you expended goes into thermal energy of the block and the table. There is no kinetic energy change because that involves the total force and in this example we ignored the force of friction because we were only interested in the energy that you expended so we could determine how much of that energy went into thermal motion.

I just noticed that I never created a webpage to describe this. I've got my work cut out for me I see?