A boy standing on a moving truck throws a projectile such that he is able to catch it back after the truck has moved 100 m. If the truck is moving horizontally along a straight line with a constant speed 30 m/s, at what speed (relative to the truck) must the projectile is thrown. (Assume, `g = 10 m//s^2` )

Options

A. `55/3 m//s`
B. `43//2 m//s`
C. `50/3 m//s`
D. `23/2 m//s`

Answer

C

Explanation

Given, velocity of truck, v = 30 m/s
time taken by truck to move a distance of 100 m.
` t = 100/30 rArr t = 10/3 s`
If `v_1` be the velocity of projectile in upward direction then time taken by the projectile to reach at maximum height is ` t_1` then
`0 = v_1 - gt `
` v_1 = gt_1`
But ` t_1 = t/2 = 3/2 = 5/3 s `
` therefore v_1 = g xx 5/3 = (10 xx 5)/(3) = 50/3 m//s `