Kinetic Energy: The energy possessed by an object due to its motion is called kinetic energy.
Example of Kinetic Energy:
(i) A falling coconut
(ii) a speeding car
(iii) a rolling stone
(iv) a flying aircraft
(v) flowing water
(vi) blowing wind
(vii) a running athlete
(viii) A moving cricket ball
Main-points:
- A moving object can do work.
- An object moving faster can do more work than an identical object moving relatively slow.
- The kinetic energy of a body moving with a certain velocity is equal to the work done on it to make it acquire that velocity.
Formula for Kinetic Energy:
Consider an object of mass, 'm' moving with a uniform velocity, 'u'. Let it now be displaced through a distance 's' when a constant force, F acts on it in the direction of its displacement.
Its velocity changes from 'u' to 'v'. Then accelaration is 'a'.
Work done, W = f × s ......... (i)
and f = ma ......... (ii)
Now W = ma × s .......... (iii)
According to third equation of motion
2as = v2 - u2
So, s = v2 - u2 / 2a ......... (iv)
Now putting the value of s from (iv) in equation (iii)
if u = 0 (When the body or an object starts moving from rest)