A stone thrown upward from the top of a 320-foot cliff at 128 ft/sec eventually

Question

A stone thrown upward from the top of a 320-foot cliff at 128 ft/sec eventually falls to the beach below.

a) How long does the stone take to reach its highest point?

b) What is its maximum height?

c) How long before the stone hits the beach?

d) What is the velocity of the stone on impact?

Please don't copy and paste from other websites, I already searched on google for answers, and i found many, but i still don't understand how to solve it. Please show all your steps and explain explain them and tell me which formulas you used. Thanks in advance.

Explanation / Answer

a)

At peak point velocity=0

v=u+at

u=128

a=-g=-32

v=0

128=32*t

t=4 s

b)

v^2-u^2=2aS

0-128*128=2*-32*h

h=256 ft

c)

Total time=t

S=-320

u=128

a=-g=-32

S=ut+at^2/2

-320=128*t-32*t^2/2

t=10 sec

d)

v=u+at

=128-32*10

=-192 ft/s

or 192 ft/s downwards

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