A tunnel is dug along a diameter of the earth. Find the force on a particle of mass m placed in the tunnel at a distance x from the centre.

Answer

C

Explanation

Mass of earth `M=(4/3)piR^3rho`
mass of the imagiN/Ary sphere having
`radius =x, M'=(4/3)pir^3rho`
`rarr M'/M =x^3/R^3 `

`:. Gravitational force on f
=(GMm)/x^2`
`rarr F=(GMx^3m)/(R^3x^2)=(GMm)/R^3x`