A stone weighing 1 kg is dropped from rest from a height of 4 metres above the ground. When it has free-fallen 1 metre its total energy with respect to the ground is:

1. 15 J
2. 40 J
3. 20 J
4. 30 J

 Here, the mass of the stone $m=1\ kg.$

Height of the stone $h=4\ m$

Let's take $g=10\ m/s^2$

Therefore, at the height of $4\ m$, the total energy is the potential energy$=mgh$

$=1\ kg\times10\ m/s^2\times4\ m$

$=40\ J$

After falling 1 meter, total energy will be the same $40\ J$ according to the law of the conservation of the energy.

Therefore, option b). is correct.

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Updated on: 10-Oct-2022

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