A) Estimate how long it took King Kong to fall straight down from the top of the Empire State Building (380 m high). Express your answer using two significant figures.

b) Estimate his velocity just before "landing." Express your answer using two significant figures. Assume that the positive direction is upward.

a) 8.8 sec b) - 86 m/sec

Explanation:

Assuming King Kong started from rest its fall, once in the air, neglecting air resistance, is only affected by gravity, which accelerates it downward.

As this acceleration is constant, we can use the following equation in order to get how long it was falling:

Δh = 1/2*g*t² ⇒ - 380 m = 1/2 (-9.8 m/s²) * t²

Solving for t:

t = √ ((2*380) / 9.8) s² = 8.8 sec.

b) In order to know the value of the velocity in the instant just before it hits the ground, we can apply acceleration definition, as follows:

a = (vf-v₀) / t

In our case, a = - g (assuming positive direction is upward) and v₀=0, so, we can solve for vf as follows:

vf = - g*t = - 9.8 m/s²*8.8 sec = - 86 m/s.