Question

A mass m₁ is placed at the centre of a shell of radius R, m₂ is placed at a distance R from the surface and is immersed in an oil of dielectric constant 10. Find the force on m₁.

• A. Zero
• B. $\frac { \mathrm { G } \left( \mathrm { M } + \mathrm { m } _ { 2 } \right) \mathrm { m } _ { 1 } } { 10 \mathrm { R } ^ { 2 } }$
• C.
• D. $\frac { G m _ { 1 } \left( 4 M + m _ { 2 } \right) } { 4 R ^ { 2 } }$

Answer 1

Answer: (C)

Answer 2

$\frac { \mathrm { GM } _ { 1 } } { \mathrm { x } ^ { 2 } } = \frac { \mathrm { GM } _ { 2 } } { ( 1 - \mathrm { x } ) ^ { 2 } }$ or $\frac { 1 - \mathrm { x } } { \mathrm { x } } = \frac { \sqrt { 2 } } { 1 }$ or x = $\frac { 1 } { \sqrt { 2 } + 1 } = 0.4 \mathrm {~m}$