A construction worker dropped a brick from a high scaffolding. How fast was? a. How fast was the brick moving after 4.0 s of falling? b. How far did the brick fall after 4.0 s of falling?

A) How fast was the brick moving after 4s?

Vf=?

Vi=0 (because it was dropped, not thrown)

A = - 9.8m/s^2 (gravity)

t = 4s

Use the equation Vf=Vi+A (t)

Vf=0 + (-9.8) (4)

Final answer: Vf = - 39.2m/s

b) How far did the brick fall after 4s?

D=?

Vi=0

t=4s

A=-9.8m/s2

**You do have the final velocity, but it is best to avoid using numbers that you have calculated yourself.**

Use the equation: d=Vi (t) + 0.5 (A) (t) ^2

d = (0) (4) + 0.5 (-9.8) (4) ^2

d = (-4.9) (16)

d=-78.4m

Therefore, after 4s the brick fell 78.4m