# JEE Class main Answered

**law of conservation of energy in case of freely falling body**

Asked by mdowaisraza581 | 16 May, 2023, 10:06: PM

Expert Answer

Let the body is dropped from height h . Just before dropping it has only potential energy (mgh) ,

where m is mass of body, g is acceleratio due to gravity and h is height.

Hence intial total energy E

_{i}is ................................... (1)

Let us consider it has fallen a distance y from initial point .

Potential energy U at this point is

...............................(2)

Speed of body at this point is determined from the following equation

Hence kineti energy K at this point is

Total energy E

_{y}at this point is sum of potential energy and kinetic energy ...........................(3)

Finally, when the body reaches ground , its potential energy is zero and has only kinetic energy.

Final kinetic energy K

_{f}iswhere v

_{f}is the final speed when body reaches the ground.Final speed v

_{f}is determined from the following equationHence final kinetic energy , or total energy at ground is

......................................(4)

Hence from eqn.(1) , eqn.(3) and eqn.(4) , we see that total energy always remain same as ( m g h ) .

This is due to conservation of energy. At a height h, all total energy is in the form of potential energy.

After falling a distance y from starting point , potential energy decreases but kinetic energy increases .

We found that sum of potential energy and kinetic energy is ( m g h ) .

When the body is reaching ground, just before hitting the ground , it has only kinetic energy that equals ( m g h ) .

Hence loss in potential energy equals gain in kinetic energy so that sum of kinetic enrgy and potential energy at all the points is same.

Answered by Thiyagarajan K | 17 May, 2023, 11:27: AM

JEE main - Physics

Asked by theavengers0203 | 24 May, 2023, 08:40: AM

ANSWERED BY EXPERT

JEE main - Physics

Asked by mdowaisraza581 | 16 May, 2023, 10:06: PM

ANSWERED BY EXPERT

JEE main - Physics

Asked by swayamagarwal2114 | 21 Jul, 2022, 05:17: PM

ANSWERED BY EXPERT

JEE main - Physics

Asked by vishal.vini86 | 22 Apr, 2022, 12:06: AM

ANSWERED BY EXPERT

JEE main - Physics

Asked by pratham.k | 02 Jun, 2020, 12:20: AM

ANSWERED BY EXPERT

JEE main - Physics

Asked by Vedantshinde4may | 25 Feb, 2019, 05:10: PM

ANSWERED BY EXPERT

JEE main - Physics

Asked by Reetusahrey | 07 Feb, 2019, 07:36: PM

ANSWERED BY EXPERT

JEE main - Physics

Asked by rsudipto | 03 Jan, 2019, 12:54: PM

ANSWERED BY EXPERT