Question

a stone is thrown vertically upward with an intial velovity of 12m/s, after some time it returns to the same position
a)what is the displacement of the stone
b)the highest point it reached if it took 2 seconds for the stone to reach this point
c)the kinetic energy of the stone
d)the potential energy of the stone at the highest point

Answer 1

a)
Displacement is the vector from the start point to the finish point.
We ended up where we started.
So
ZERO !!!! (this was a trick question)

b)
I guess we do not know that g = 9.81 m/s^2 or we would not need that 2 seconds given.

v = Vi - g t
at top v = 0
Vi = g t = 2 g
12 = 2 g
g = 6 m/s^2 (some other planet)
but anyway
h = Hi + Vi t -(1/2)g t^2
h = 12 (2) -(1/2)(6)(4) = 24 -12
h = 12 meters on this planet

c) the max Ke = (1/2)(m)(12)^2
= 72 m

d) max Pe above the thrower
= m g h = m (6)(12) = 72 m
of course because max Ke = max Pe

This question is very strange. Did you get it from a text or did you make it up?