A hole is bored in a straight line though the Earth from A to B a ball-bearing is dropped at end A. Assuming that frictional and air resistance are negligible, and that the Earth may be taken to be uniform-density sphere of radius 6400 km, how long does it take the ball bearing to arrive at B ? [Neglect any effects due to the rotation of the Earth, and assume the acceleration due to gravity at the Earth's surface to be 9.8 ms–2.]
(A) 2.5 × 103 s
(B) 3.5 × 103 s
(C) 3.0 × 103 s
(D) 3.2 × 103 s
