Discussion Forum

 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/s²)

Answer:

Explanation:

Given, velocity of truck, v=30 m/s

 time taken by truck to move a distance of 100 m

 $t= \frac{100}{30}\Rightarrow$  $t= \frac{10}{3} s$

 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, $t_{1}=\frac{t}{2}=\frac{\frac{10}{3}}{2}=\frac{5}{3}s$

 $\therefore$   $v_{1}=g\times \frac{5}{3}=\frac{10 \times 5}{3}=\frac{50}{3} m/s$