Question

A stone is projected horizontally with speed $10m/s$ from a height $h$ above the ground. A horizontal wind is blowing in the direction opposite to the velocity of projection and gives the stone a constant horizontal acceleration $10m/s^2$ (in the direction opposite to the initial velocity). As a result the stone falls on ground at a point vertically below the point of projection. Then the value of height $h$ is ($g=10m/s^2$)

• A. 10 m
• B. 20 m
• C. 50 m
• D. None of these

Answer 1

The correct option is B 20 m

Time taken to reach the ground is given by
$h=\frac{1}{2}g{t}^2$--------(1)
Since horizontal displacement in time t is zero
$\therefore t=\frac{2V}{f}$-------(2)
$h=\frac{2g{v}^2}{f^2}=20m$