A ball is thrown from the ground with velocity of 30m/s after what time has the ball has velocity of 10m/s down ward?

a ball is thrown vertically upward from the ground with the velocity of 30m/s. a) how long will it take to rise to its highest poitn? b) how high does the ball rise? c) how long after projection will the ball have a velocity of 10m/s? d) what is the total time of flight?

From Vf = Vo - gt, 0 = 30 - 9.8t yielding t = 3.06 sec.

From h = Vo(t) - g(t^2)/2, h = 30(3.06) - 4.9(3.06)^2 yielding h = 45.88m.

From Vn = Vo - gt, 20 - 9.8t yielding t = 2.04 sec.

Since the fall time equals the rise time, the total flight time is 2(3.06) = 6.12 sec.

positive reinforcement? ?