Question

A stone with a mass of 2kg is thrown vertically upwards.it takes 5 seconds for the stone to reach the same height from which it was thrown. Determine th following:3.2.1 the volocity with which the stone was thrown

Answer 1

We can assume the rock was thrown from a height of 0.

So, now you know that
h(t) = vt-5t^2
h(5) = 0, so
5v-125 = 0
v = 25 m/s

Answer 2

note that the energy all together is the relationship between potential and kinetic energy
mgh=1/2mv2

v=u+at.. lest u is zero and a is 9.81 as t is 5. so v=49m/s
but note that by the law of conservation of energy above then make h the subject you get h=(1/2)(v2)/g.....we kno v and g ...so h=is 125 to three significant figures