4.5 You are on the roof of a tall building. Your TA (who is 1.8m tall) is walkin

Question

4.5 You are on the roof of a tall building. Your TA (who is 1.8m tall) is walking by, and you drop (from rest at the level of the roof) a water balloon on him. It takes 2s for the balloon to go from the roof of the building to your TA’s head. (a)[6 pts] How tall is the building? (b)[5 pts] What was the velocity of the balloon when it hit your TA? (c)[8 pts] If instead of dropping the balloon from rest, you threw it down (speed 10 m/s straight down as it passes the roof level), how fast would it be traveling when it hits your TA and how long would it take? (d)[5 pts] If the building was twice as tall, how long will it take an object dropped from rest (at roof level) to hit the ground?

Explanation / Answer

A.)

S= ut + 0.5 a t^2

s =0 + 0.5 * 9.81 * 4 = 19.62 m

height of building = 19.62 + 1.8 =21.42 m

b.) v = u+at

v = 0 + 9.81*2 = 19.62 m/s

c.) v^2 = u^2 + 2as

v^2 = 10^2 + 2*9.81*19.62

v = 22.02 m/s

d.)height of building = 2* 21.42 = 42.82 m

s = ut + 0.5at^2

42.82 = 0.5 *9.81*t^2

t 0 2.9546 sec

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