The force of gravity on a 2 kg rock is twice as great as that on a 1 kg rock. Heavier fall faster?

Question

The force of gravity on a 2 kg rock is twice as great as that on a 1 kg rock. Why then doesn’t the heavier rock fall faster?

Answer 1

Force equals mass times acceleration. The force is doubled, and the mass is doubled, but the acceleration is therefore the same (e.g. gravity).

F = ma
a = F/m

2F = 2ma
a = 2F/2m
a = F/m

So in either case the rock falls at the same rate of acceleration, thus the rock with the higher mass falls at the same rate as the one with the lower mass. (Obviously we are discounting air resistance, etc.)

Answer 2

The force of gravity on a 2 kg rock is twice as great as that on a 1 kg rock. BoTH will fall at a same rate.

(Heavy objects and light objects have to fall the same way, because conservation laws are additive --- we find the total energy of an object by adding up the energies of all its atoms. If a single atom falls through a height of one meter, it loses a certain amount of gravitational energy and gains a corresponding amount of kinetic energy. Kinetic energy relates to speed, so that determines how fast it's moving at the end of its one-meter drop. (The same reasoning could be applied to any point along the way between zero meters and one.)

Now what if we stick two atoms together? The pair has double the mass, so the amount of gravitational energy transformed into kinetic energy is twice as much. But twice as much kinetic energy is exactly what we need if the pair of atoms is to have the same speed as the single atom did. Continuing this train of thought, it doesn't matter how many atoms an object contains; it will have the same speed as any other object after dropping through the same height.)

Answer 3

The Tale of Galileo and the Tower of Pisa
The story goes that in order to demonstrate to Aristotlean scholars that two balls of different weights fall at the same rate, Galileo dropped a cannon ball and wooden ball from the top of the Tower of Pisa.

This story is apocryphal. While some of his earlier predecessors actually performed this experiment, Galileo did not. However, when Galileo was an old man, one of his students did perform the demonstration to an audience of Aristotlean scholars and found in fact a slight difference in the time the two balls struck the ground. This came as no surprise to Galileo who had already explained the effects of viscosity (wind friction) years before.

Apollo 15 Astronaut David Scott perform Galileo's experiment on the Moon. Galileo's hypothesis had been that all objects fall with the same acceleration in the absence of air resistance.

Answer 4

It takes more force to get a massive object like a steamroller to start or stop than a less massive object.
.
The force of gravity may be twice as great on the 2 kg rock, but it's also twice as hard to accelerate or decelerate.

Answer 5

Because gravity is stronger between the heavier rock and earth, but the heavier rock also has more inertia in it's "rest" state so the gravtitational force is fighting against more inertia.

Answer 6

Ah yes but the two kg mass accelerates less fast with the same force

Answer 7

Terminal velocity is the speed at which acceleration ceases and the fall is then at the same velocity until just before impact. The reason your looking for is a=fm accel. = forceXmass.

Answer 8

gravity does not depend on
THE MASS OF THE OBJECT
if you drop a feather and a hammar on moon, they will reach the ground at the same time

Answer 9

This logical fallacy was disproven by Gallileo in the 14th century.
The answer is: because it has twice the mass.

a = F/m

Answer 10

nope it falls at the same speed. its called terminal velocity.