Question

Assume the earth is a uniform sphere of mass M and radius R. As strange as it may sound, if one can dig a long tunnel from one side of the Earth straight through the center and exit the other end, any object falling into the tunnel will appear at the other end (i.e. the opposite side of the Earth) in just 2530 s (42.2 min). Call that time t. Let t be a function of G, M, and R, where G = 6.67 x 10^-11 m³ kg⁻¹ s⁻² is the Universal Gravitational Constant, M = 5.98 x 10^24 kg, and R = 6400 km.

(a) From dimensional analysis alone find the expression for t, up to a numerical constant c.
(b) Determine the value of c by using the above values in the expression found in part (a).

Answer 1

Solution