A dynamite blast at a quarry launches a rock straight upward, and 1.5 s later it is rising at a rate of 19 m/s. Assuming air resistance has no effect on the rock, calculate its speed (a) at launch and (b)4.6 s after launch.

Answer 1

V = Vo - gt = +19 m/s at t = 1.5
(a) Solve for Vo
Vo = 19 + 9.8*1.5 = 33.7 m/s

(b) Plug in t = 4.6 in the first formula and solve for V, which will be negative.

Answer 2

-11.38