As shown in figure. When a spherical cavity (centred at O ) of radius 1 is cut out of a uniform sphere of…

As shown in figure. When a spherical cavity (centred at O ) of radius 1 is cut out of a uniform sphere of radius R (centred at C ), the centre of mass of remaining (shaded part of sphere is at G, i.e., on the surface of the cavity. R can be determined by the equation:
  1. R2+R+12-R=1
  2. R2-R-12-R=1
  3. R2-R+12-R=1
  4. R2+R-12-R=1

Solution

M1=43πR3ρ
M2=43π13-ρ
Xcom=M1X1+M2X2M1+M2
43πR3ρ0+43π13-ρR-143πR3ρ+43π13-ρ-2-R
R-1(R3-1)=2-RR1
R-1R-1R2+R+1=2-1
R2+R+12-R=1
Alternative:
Mremaining2-R=Mcavity1-R
R3-132-R=13R-1
R2+R+12-R=1

Asked in: JEE Main 2020 (08 Jan Shift 2)

Practice more Center of Mass Momentum and Collision questions on Aicharya