A tunnel is dug through the centre of the Earth. Show that a body of mass ‘m’ when dropped from rest from one end of the tunnel will execute simple harmonic motion.
We know that,
Acceleration due to gravity inside the earth = g’
=
Now, R-d = y
Thus,
On both of them, force at depth ‘d’ will be –
Thus, in the tunnel, the motion of the body is SHM.
We can say,
Thus,
Or, .