Energy of an electron in the second orbit of hydrogen atom is E and the energy of electron in 3rd orbit of He will be

Explanation

Here tension produced due to the haning part of the rope.
The torque `(tau)` acting on the cylinder due to the tension.
`tau=RT=Ialpha`
`therefore alpha=(RT)/(I)….(1)`
Now, the moment of inertia about the axis of system,
`I=mR^(2)+(MR^(2))/(2)....(2)`
Note that the whole mass of the rope is at distance R from the centre of cylinder
Now `T=x` = weight of the rope
`therefore T=(m)/(l)xg....(3)`
putting the value of (1) from eqn. (2) and value of T from eqn. (3) in eqn. (1), we have
`alpha=(R((m)/(l))xg)/(mR^(2)+(MR^(2))/(2)),therefore alpha=(2mgx)/(Rl(M+2m))`