Question

From the top of a tower $19.6$ m high, a ball is thrown horizontally. If the line joining the point of projection to the point where it hits the ground makes an angle of ${45}^o$ with the horizontal, then the initial velocity of the ball is?

• A. $9.8$ $m{s}^{-1}$
• B. $4.9$ $m{s}^{-1}$
• C. $14.7$ $m{s}^{-1}$
• D. $2.8$ $m{s}^{-1}$

Answer 1

The correct option is A $9.8$ $m{s}^{-1}$

Given height h=19.6 m; $\theta$=${45}^0$

We know time$=\sqrt{\frac{2h}{g}}=\sqrt{\frac{2\times 19.6}{9.8}}=\sqrt{4}=2$

Also we know velocity $=\frac{Distancetravelled}{Time}=\frac{19.6}{2}=9.8m/s$