As you are cycling to classes one day, you pass a construction site on Green Str

Question

As you are cycling to classes one day, you pass a construction site on Green Street for a new building and stop to watch for a few minutes. A crane is lifting a batch of bricks on a pallet to an upper floor of the building. Suddenly, a brick falls off the rising pallet. You clock the time it takes the brick to hit the ground at 2.5 seconds. The crane, fortunately, has height markings, and you see the brick fall off the pallet at a height of 22 meters above the ground. A falling brick, as we all know, can be dangerous, and you wonder how fast the brick was going when it hit the ground. Since you are taking physics, you quickly calculate the answer.

Explanation / Answer

Initial Velocity

h = -(1/2)*g*t2 + Vo*t   

V0 = {(1/2)*g*t2 – h}/t

V0 = {(1/2)*9.81*2.52 – 22}/2.5

V0 = 3.4625 m/s

velocity of the brick striking the ground

V = Vo – g*t

V = 3.4625 – (9.81*2.5)

V = -21.0625 m/s (going down)

V = 21.06 m/s

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