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Nuclear Fission and Fusion – A Facebook conversation

Find below a conversation between Master Deepak, PUC student and Mr. Mathew Abraham, Physics teacher.

Deepak asked: “nuclear fusion or fission in which of these energy released is more and why?”


Energy released per fission is more than energy released per fusion. But energy released per unit mass during fusion is very much greater than energy released per unit mass during fission


But why energy released is more


The fission of a U-235 releases about 200 MeV of energy
whereas the fusion of 4H to form He releases only about  20 MeV
But, the 200 MeV is obtained from 236 amu
and the 20 MeV is obtained from just 4 amu


Then why dont we use nuclear fusion as source of energy and electricity



Nuclear fusion requires very high temperature to start. It is difficult to maintain such a huge temperature (of the order of million degrees).

Tokamak magnetic field and plasma current.
Tokamak magnetic field and plasma current. (Photo credit: Wikipedia)

Research is going on to construct nuclear fusion reactor

The international prototype is named tokamak
In that the nuclear fusion is carried out in plasma state held at high temperature confined in magnetic field produced by huge torroidal solenoids


Bouncing ball and energy dissipation problem

Please help me with the question below.. I’m totally confused!

Bouncing Ball - bad animation example

A player throws a ball of mass 0.6 kg into the air, to a height of 4.0 m above the ground. The ball then falls to the ground. During the impact, 22% of the ball’s energy is lost. Calculate the height to which the ball rises after the bounce. Your assistance will be appreciated..

Mustafa posted


m= 0.6 kg

h = 4.0 m

Energy = mgh

During impact 22% energy is lost. Therefore, energy remaining = 88%

Therefore the energy with which the ball rebounds = 24 x 88/100 J

This is equal to the potential energy at the highest point after bouncing

If the new height is h’

mg h’ = 88% mgh

h’ = 0.88 x h = 0.88 x 4.0 =3.52 m

If you have further doubts, please ask

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April 2021

Schrodinger’s Cat in Daily Life

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