Question

A ball is projected from a point O as shown in figure. It will strike the ground after ($g = 10m/s^2$)

• A. 4s
• B. 3s
• C. 2s
• D. 5s

Answer 1

Answer: (A)

4s

Answer 2

The problem involves projectile motion from a height. We decompose the initial velocity into vertical and horizontal components. The vertical motion is governed by gravity. By considering the initial height as 0 and the ground as -60m (or vice versa), and using the kinematic equation $s = ut + \frac{1}{2}at^2$ for vertical displacement, we form a quadratic equation in time. Solving this quadratic equation yields two values for time, one positive and one negative. The positive value represents the physical time taken for the ball to reach the ground.