Question

Q1.A body of mass 20 kg is initially at a height of 3 m above the ground . It is lifted to a height of 2 m from that position. Its increase in potential energy is (a) 100 J (b) 392 J (c) 60 J (d) -100 J​

Answer 1

Answer:

392J

Explanation:

solution given in figure,,,,

Answer 2

Answer:

(B)The increase in potential potential energy of the body is 392.4J

Explanation:

Given that,

A body of mass 20kg is initially at a height of 3m above the ground and then it is lifted to a height of 2m from that position.

We have to find the increase in potential energy of the body.

We know that potential energy of a body is the product of its weight and the height through which it is lifted.Therefore,we write it mathematically as

$P.E=Wh=mgh$

The given data is written as follows by assigning their symbols.

The initial height is $h_{i}=3m$

And the final height is provided as $h_{f}=3+2=5m$

Also the mass is provided as $m=20kg$

Therefore,the initial potential energy is calculated as$P.E_{i}=mgh_{i}=20\times9.81\times3=588.6J$

And the final potential energy is

$P.E_{f}=mgh_{f}=20\times9.81\times5=981J$

Therefore,the change in potential energy is found to be $\triangle P.E=981-588.6=392.4J$

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