Question

A particle is fired horizontally with a velocity $98m{s}^{-1}$ from the top of a tower 490m high. The time taken by the projectile to hit the ground is:$:\left(g=9.8m/s^2\right)$

• A. 2 s
• B. 5 s
• C. 10 s
• D. 20 s

Answer 1

The correct option is C 10 s

$h=490m,u_x=98m/s,u_y=0m/s$

using 2nd equation of motion in Y direction

$s_y=u_{y}t+\frac{g{t}^2}{2}$

$h=\frac{g{t}^2}{2}$

$t=\sqrt{\frac{2h}{g}}$

$t=10s$