Question

A ball is thrown off a high cliff with no horizontal velocity. It lands 6.0 s later with a velocity of 40m/s. What was the initial velocity of the ball? 

(A) 100 m/s up 

(B) 20 m/s up 

(C) 0 

(D) 20 m/s down 

(E) 100 m/s down

Answer 1

Correct option (B) 20 m/s up

v_f = –40m/s (negative since it is moving down when landing). Use v_f = v_i + (–g)t.