Question

a boy throws a stone upward with a velocity of 60m /s.
a) how long will it take to reach the maximum height
(g = - 10m /s ^2)
b) what is the maximum height reached by the ball
c) how long will it take to reach the ground

Answer 1

B, v2-u2=2gh
02-60 2=2*10*h
3600/2*10=h
=180
A, h=ut+1/2gt2
180=60*t+1/2*10*t2
180=60*t+5*t2

Answer 2

Given :

A stone is thrown upward with a velocity of 60 m/s .

$g=-10\ m/s^2$ .

To Find :

Maximum height reached and time taken to reach ground .

Solution :

We know , by equation of motion .

$v^2-u^2=2as\\s=\dfrac{v^2-u^2}{-2g}\\\\s=\dfrac{u^2-v^2}{2g}\\\\s=\dfrac{60^2-0^2}{2\times 10}\\\\s=180 \ m$

Now , time taken to reach ground .

$v=u+at\\-60=60-gt\\t=12\ s$

Hence , this is the required solution .