(4) A firefighter is standing on top of a building 19 m high, holding a firehose

Question

(4) A firefighter is standing on top of a building 19 m high, holding a firehose 1 m above the top of the building. She finds that if she holds the hose horizontally the water flows from it at 12 m/s. As this hapens the water hits an adjacent burning building at a height of 15 m above the ground. (The gravity constant is 9.8 m/s2. ) What is the horizontal distance from the firefighter to the building? (The next page has some additional parts that may help guide you through one po tential solution to this problem.)

Explanation / Answer

a] 2D

b] a(t) = -g j = -9.8 m/s^2 j

c] vo = 12 m/s i

v(t) = 12 m/s i -9.8t m/s j. where t is in s

so = 20 m j

s(t) =  (20 - 4.9t^2) m j + 12t m i where t is in s

d] 15m j = (20 - 4.9t^2) m j

t = sqrt(5/4.9) = 1.01 s

e] distance s = 12*1.01 = 12.12 m answer

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