Two identical metal coins are dropped separately into two identical tubes. One of the tubes if filled with air and the other has its air pumped out with a vacuum pump.
Which of the following observation(s) is/are true?
a. Both metal coins will drop with same speed
b. Both metal coins will accelerate at a different rate
c. Both metal coins will reach the bottom of the tube at the same time
Answers
When two objects of the same mass are allowed to freely fall in vacuum by virtue of gravity, they will fall at the same accelerated velocity. This is because the gravitational field causes them to accelerate and this has nothing to do with the objects’ masses. The acceleration due to gravity is approximately a constant, around 9.8 m/s^2 near the earth’s surface and does not depend on any of the masses. Even if you drop a feather and a solid metal ball (objects of different masses) from the same height in a vacuum chamber, they will fall at the same rate.
The weights when measured, will approximately be the values of the weights when measured normally. Usually, we displace the air on top of the weighing machine causing it to exert upward pressure on us. Without the upward pressure due to air, the weighing machines will show a slightly larger number than normal.