Question

A fire hose shoots water horizontally from the top of a building toward the wall of a building 20 m away. If water leaves the hose at 5.0 m s-1, how far below the hose level does it strike the wall?

Answer 1

Given info : A fire hose shoots water horizontally from the top of a building toward the wall of a building 20 m away. If water leaves the hose at 5.0 m/s.

To find : How far below the hose level does it strike the wall ?

solution : it is based on concept of horizontal projectile motion.

horizontal speed of fire hose, u = 5 m/s

let after time t, it will strike the wall.

so horizontal distance covered by fire hose, x = ut = 5t

x = 20 = 5t ⇒t = 4 sec

vertical speed of fire hose, u = 0

acceleration acting along vertical direction on the fire hose.

so, acceleration, a = g = 10 m/s²

using formula, y = ut + 1/2 at²

⇒y = 0 + 1/2 × 10 × (4)²

= 1/2 × 10 × 16

= 80 m

Therefore the fire hose 80 below the hose level strikes the wall.