Question

A boy wants to throw a paper wrapped over a stone to his friend across the street 40m wide.the boy window is 10m below the friend window .how should he throw the ball?

Answer 1

Hello Dear,

◆ Answer -

The boy should throw the stone at 31.3 m/s at angle of 26.57° with horizontal.

◆ Explanation -

This can be illustrated as projectile motion of the stone.

For successful throwing of the stone in friend's window,

1. Horizontal range should be double that of 40 m. i.e. R = 80 m
2. Maximum height need to be 10 m. i.e. H = 10 m

Now we have to calculate angle of projection,

tanθ = 4H/R

tanθ = 4 × 10 / 80

tanθ = 1/2

θ = arctan(1/2)

θ = 26.57°

To calculate initial velocity, we'll use formula -

R = u².sin2θ/g

80 = u² × sin(2×26.57) / 9.8

u² = 80 × 9.8 / 0.8

u² = 980

u = 31.3

u = 31.3 m/s

Thus, boy should throw the stone at 31.3 m/s at angle of 26.57° with horizontal.

Thanks dear...