Question

A ball is projected horizontally from the top of the building $19.6m$ high. If the line joining the point of projection to the point where it hits the ground makes an angle of ${45}^{\circ }$ to the horizontal, the initial velocity of the ball is

• A. $4.9m/s$
• B. $9.8m/s$
• C. $19.6m/s$
• D. $14.7m/s$

Answer 1

The correct option is B $9.8m/s$

$\begin{array}{c}{v}_{xi}=u\\ v_{yi}=0\\ T=\frac{2h}{g}=\frac{2\times 19.6}{9.8}=2\sec \\ R=V_{xi}T\\ V_{xi}=u=\frac{R}{T}=\frac{19.6}{2}=9.8m{s}^{-1}\end{array}$

Hence option (B) is correct.