Question

A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 m/s. What will be is
potential energy at the end of 2 s? (Assume g = 10 m/s2).
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Answer 1

Answer:

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Given,

Mass of the body, m = 2kg,

Initial velocity, (u) = 20 m/s,

Time, (t) =2s,

Acceleration due to gravity, g = 10 m/s.

Let the height at the end of 2s = d

We know that,

d = ut + 1/2at2

d = 20 x 2 + 1/2 x (-10) x (2)2

d = 40- 20

d = 20m

(g is taken as negative because it is acting in the direction opposite to the direction of motion)

Potential Energy, P.E = mgh

= 2 × 10 × 20

= 400 J.

Answer 2

Initial velocity is 20 m/s , mass of body is 2 kg.

So lets find out the height upto which the ball goes after 2 seconds :

$h = ut - \frac{1}{2} g {t}^{2}$

$= > h = (20 \times 2) - \frac{1}{2} \times 10 \times {(2)}^{2}$

$= > h = 40 - 20$

$= > h = 20 \: m$

Potential Energy is the Gravitational Energy possessed by the virtue of its position with respect to the position in the Earth's Gravitational Field.

PE = m × g × h = 2 × 10 × 20 = 400 J.

So final answer is 400 J