Question

A car is moving horizontally along a straight line with a uniform velocity of $25m/s$. A projectile is fired vertically from car such that it returns to it, when car has moved $100m$. The projected speed $(g=10m/s^2)$

• A. $80m/s$
• B. $20m/s$
• C. $30m/s$
• D. $5m/s$

Answer 1

The correct option is B $20m/s$

Given,

$v_x=25m/s$

$x=100m$

Time required, $T=\frac{x}{v_x}$

$T=\frac{100}{25}$

$T=4s$

So, Time of flight is $4s$.

$T=\frac{2usin\theta }{g}$

$usin\theta =\frac{Tg}{2}$

$usin\theta =\frac{4\times 10}{2}$

$v_y=20m/s$

The correct option is B.