A short , straight and frictinless tunnel is bored through the centre of the earth and a body is realesed from the surface into the tunnel . Show that the motion of the body in the tunnell will be simple harmoic and hence calculate the taken by the body to travel from one end of the tunnel to the other (Radius of the earth = `6.38 xx 10^(6)m` and acceleration due to gravity at the surface = `9.81 ms^(2)`

Answer

`42` min `14 s`