A stone dropped from a helicopter passes a tall vertical glass building. It takes 2 s to cross the entire height of the building. The velocity of the stone at the bottom of the building is exactly three times its

Question

Quantrex Academy · Accepted Answer

Correct answer: A. 40 m

Let the velocity of the stone at the top of the building be

u

.

The velocity at the bottom of the building is given as

v = 3u

.

Using the first equation of motion,

v = u + gt

for the motion across the building:

3u = u + (10)(2)

2u = 20 \Rightarrow u = 10\text{ m s}^{-1}

Now, use the second equation of motion to find the height of the building (

s

):

s = ut + \dfrac{1}{2}gt^2

s = (10)(2) + \dfrac{1}{2}(10)(2)^2

s = 20 + 20 = 40\text{ m}

Answer:

40\text{ m}

A stone dropped from a helicopter passes a tall vertical glass...

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