A projectile A is projected from ground. An observer B running on ground with uniform velocity of magnitude 'v' obseryes A to move along a straight line. The time of flight of A as measured by B is T. Then the range R of projectile on ground is
The horizontal and vertical components of initial velocity of projectile are as shown in figure. Since the observer moving with uniform velocity v sees the projectile moving in straight line
Hence v = u
The time of flight as measured by observer B T =
Hence horizontal range of projectile on ground
R = ()T = vT