Question

A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 m/s. What will be its potential energy at the end of 2 s ? (Assume g = $10m/s^2$).

Answer 1

Given that,

mass of the body, m= 2 kg

Initial velocity, u = 20 ms \frac{m}{s} sm​

time taken = 2 s

acceleration due to gravity, $g=-10m/se{c}^2$

Height covered by the body in 2s is given by the second equation of motion that is

$h=ut+\frac{1}{2}a{t}^2$

$=(+20)\left(2\right)+\frac{1}{2}(-10)\left(4\right)$

$=40-20$

$h=20m$

s=ut+12gt2s = ut + \frac{1}{2} gt^2

Potential energy of the body after 2s = mgh = $s=2\times 10\times 20$ = $400J$