A body projected with some initial velocity and then allowed to fall only under gravity is called a projectile.
Assumptions made in the study of projectile motion:
(i) Acceleration due to gravity ‘g’ is constant both in magnitude and direction.
(ii) There is no resistance due to air.
(iii) The earth is flat.
(iv) Rotational motion of the earth is absent.
Horizontal velocity = u
Height of the step = h
Let the ball hit the nth step.
Therefore the ball transverses a horizontal distance of nb and falls vertically by nh.
Equation of trajectory of horizontal projectile,
Substituting y = nh and x = nb, we get,