Firemen are shooting a stream of water at a burning building using a high-pressu

Question

Firemen are shooting a stream of water at a burning building using a high-pressure hose that shoots out the water with a speed of 26.0 m/s as it leaves the end of the hose. Once it leaves the hose, the water moves in projectile motion. The firemen adjust the angle of elevation ? of the hose until the water takes 3.00 s to reach a building 46.18 m away. You can ignore air resistance; assume that the end of the hose is at ground level.

Part A

Find the angle of elevation ?.

Part B

Find the speed of the water at the highest point in its trajectory.

Part C

Find the magnitude of the acceleration of the water at the highest point in its trajectory.

Part D

How high above the ground does the water strike the building?

Part E

How fast is it moving just before it hits the building?

Explanation / Answer

2 assumptions: The firemen are at 0m height, and the water hits the building at 0m height.

the equations of projectile motion:

y = at^2/2 +vt; x = vt

if it takes 3 secs. to reach 45m . . .
46.18 = v*3 => v=15.39m/s

1)angle of water: theta = cos-1(15.39/26)
theta = 53.70 degrees

2)at highest point of trajectory, velocity of y is zero, but x component is 9m/s

3)only force acting on the water is gravity, so a=g=9.8m/s constant

4) see assumptions above, I could be wrong now

5) speed should be the same

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