(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

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 27.5 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 Θ of the hose until the water takes 3.00 s to reach a building 51.81 m away. You can ignore air resistance; assume that the end of the hose is at ground level.

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

Θ=51.1

2. Relevant equations

The equation i used to solve it was V=sqrt(v_{x}^{2}+v_{y}^{2}) and the answer was found to be 19.0 m/s

i was wondering if this equation would work to solve it? i cant get it to come out with 19 m/s though.

V_{f}^{2}= V_{yi}^{2}+2(a_{y})(Δy)

3. The attempt at a solution

V_{f}^{2}= V_{yi}^{2}+2(a_{y})(Δy)

so with this equation i used V_{yi}to be 27.5sin(51.1)=21.01

i used a_{y}to be -9.8

i used Δy to be 27.5sin(51.1)(3) + .5(-9.8)(3^{2}) = 20.11 - 0 = 20.11

(the minus 0 is because of the final height minus the initial height).

V_{f}^{2}= V_{yi}^{2}+2(a_{y})(Δy)

V_{f}= 6.87 which is definitely wrong.

Anyone know why this equation doesnt work using these numbers i calculated?

Any suggestions. Thanks :)

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# Homework Help: Can this formula be used to solve this?

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