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Q.

Two coaxial thin pipes (hollow cylinder) of radius R and 2R are having a common horizontal axis. A thin uniform hollow spherical ball of diameter R is fitted inside them as shown. The inner surfaces are sufficiently rough so that there is no slipping at contact surfaces anywhere. The outer pipe is held fixed but inner pipe is free to rotate about its axis. On slight displacement, the ball starts moving along the gap shown in the downward direction. All the 3 bodies (both pipes & ball) have same mass of 1 kg each. When ball reaches the bottom of the pipe  [Take g=10 m/s2 ]

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a

Angular speeds of inner pipe and ball about their respective axes is same.

b

Ratio of angular speeds of the inner pipe and sphere about their respective axes is  4:3

c

Ratio of KE of inner pipe to ball is 12:5

d

Net force on the ball at bottom most position is approximately  7.06 N

answer is A, C, D.

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Detailed Solution

Linear velocities (as shown) of points are w.r.t. ground and angular velocities are about respective axis of rotation passing through centre of mass. 
P is a point on outer shell in contact with spherical shell which is the instantaneous point of rest for spherical shell.
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v1=ω1R2,v=2v1&v=ω2R ω1=2v1R=vR&  ω2=vR

Hence option A is correct obviously B is wrong.

KEinner shell    =12(mR2)ω22=12mR2(vR)2=12mv2   KEball =12mv12+12{23 m(R2)2}{ω12}  =12 m(v2)2+112mR2(vR)2   =mv28+mv212=3+224mv2=5mv224   Kin,cyl Kball =12mv25mv224=12×245=125Hence, option C is correct.
For ball + inner shell as a system :
T.M.E. is conserved as there is no dissipative force within system.
mg3R=(KEball +KEshell )  at bottom,
 3mgR=5 K+12 K=17 K
(from above relation)
 K=3mgR17
where KE of inner shell
 =12 K=12×3mgR17=12mv2  v2=72gR17 (2v1)2=72gR17 v12=18gR17   =ma=m(c+τ)=m(c+0)=c  =mv12(32R) vertically upward  =2 m3R×18gR17=12mg17=12×1×1017   =12017=7.06 N vertically upward.

Hence option D is correct.
 

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Two coaxial thin pipes (hollow cylinder) of radius R and 2R are having a common horizontal axis. A thin uniform hollow spherical ball of diameter R is fitted inside them as shown. The inner surfaces are sufficiently rough so that there is no slipping at contact surfaces anywhere. The outer pipe is held fixed but inner pipe is free to rotate about its axis. On slight displacement, the ball starts moving along the gap shown in the downward direction. All the 3 bodies (both pipes & ball) have same mass of 1 kg each. When ball reaches the bottom of the pipe  [Take g=10 m/s2 ]