Physics Question?

Question

A worker drops a wrench from the top of a tower 80 m tall. What is the velocity when the wrench strikes the ground?

Answer 1

The gravitational accelaration is g = 9.8m/s^2.
we know that S = 0.5g*t^2, while v = gt
Therefore: v = gt = sqrt(g^2t^2) = sqrt(2S*g)
= sqrt(2*80*9.8) = 39.6(m/s)

Answer 2

Use relationship that H = (Vf ^2 - Vi ^2)/(2a). In your case initial speed Vi = 0 and acceleration a = g = 10 m/s^2. So 80 = Vf ^2/20. Solve by Vf - final velocity.