• An evacuated long tube contains a coin and a feather. If both objects fall together starting from the top of the tube, it is expected that: (a) the coin will reach the bottom first.
(b) the feather will reach the bottom first.
(c) both objects will reach the bottom at the same instant.

• If this experiment is repeated at a place 2000 kilometers above the sea-level, the acceleration due to gravity gexp is expected to :
(a) increase. (b) decrease. (c) remain constant.

c-) both objects will reach the bottom at the same instant.

(b) decrease.

Explanation:

Although the feather is lighter than the coin, the tube where the experiment is performed is evacuated. Therefore there is no air that prevents the feather from falling freely with the same acceleration and speed as the coin.

In fact in the equations of kinematics proposed by Newton, the mass of the bodies is not taken into account, as we can see in the following equation:

where:

Vf = final velocity [m/s]

Vi = initial velocity [m/s]

g = gravity acceleration [m/s^2]

t = time [s]

Therefore the answer is C.

Gravitational pull is a function of height, as the height of the body increases, the force of gravity decreases.