Question

A stone is thrown vertically upward from the top of a 30m high building with a velocity of 15m/s. Taking the acceleration of stone as 9.81 m/s2. And taking that as constant, determine a) the velocity v and elevations sy of stone above the ground at any time t b) the maximum altitude reached by the stone c) time when the stone strikes the ground

Answer 1

1. The upward decelerated motion
v=vₒ-gt
At the top v=0
t=vₒ/g = 15/9.8=1.53 s.
h=vₒt-gt²/2.
h= vₒ²/2g=11.5 m.
2. Free fall from the height H+h = 30+11.5 = 41.5 m.
H=gt²/2 =>
t=sqrt(2•H/g) = sqrt(2•41.5/9.8)= 2.91 s.
v=gt =9.8•2.91=28.5 m/s.
Total time =1.53+2.91= 4.44 s.