Question

an object is thrown vertically upward from top of tower with initial velocity 20m/s. it strikes the ground within 8 seconds. find height of the tower and striking velocity alo draw st, vt and at graphs.

Answer 1

Answer:

u=20m/s

T=8sec

(but actal time to get down from intial point is when the body go down again from same place ...

t=2u/g

=4sec

g=10m/s

s=ut+1/2 at²

s=80+80

s=160m.

now v²=u²-2as

v²=400-160×2×10

v²=3600

v=60m/s

Answer 2

Explanation

s =-ut+1/2at2                   given, initial velocity (u)=20m/s

s=-20+1/2gt2                            take g as 10m/s2

s=-20+1/2 x10x8x8

s= -20+320

s= 300metres

and velocity(v)= -u+gt

v= -20+10x8

v= -20+80

v=60m/s