Question

Suppose a tunnel is dug along a diameter of the earth. A particle is dropped from a point, a distance h directly above the tunnel. The motion of the particle as seen from the earth is
(a) simple harmonic
(b) parabolic
(c) on a straight line
(d) periodic

Answer 1

The motion of the particle as seen from the earth is (c) on a straight line and (d) periodic.

Explanation:

• The particle dropped at a height ‘h’ from the tunnel, travels the distance ‘h’ from the opposite side of the earth in the same direction passing through the tunnel and will return back through the same journey and at same time but in opposite direction reaching the origin point again.
• Hence, it is a periodic motion.  
• As, the tunnel is through diameter of earth and a narrow one, the motion of the particle is also a in a straight line.