A stone is thrown upwards with a velocity of 72 km/hr. If the air resistance is neglected, find the maximum height travelled by it and the time taken for it to return the initial position?
Given
initial velocity ( u ) = 72 km/hr = 72 x 1000 / 3600
= 20 m/s
acceleration due to gravity (g) = 10 m/s2
also, final velocity(v) = 0 m/s
for maximum height,
v2 = u2 - 2gH
or, 0 = 202 - 2 x 20 H
thus, H = 400/ 40
maximum height (H) = 10 m
again , for time to return to initial position.
total displacement(s) = 0
so,
s= ut - 1/2 gt2
or, ut = gt2
thus, T = u/g
= 20/10
total time taken = 2 sec