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

All objects are accelerated at a constant rate by gravity.

Explanation:

Newton's Law:

`F = ma`

Let's call the small rock `1` and the larger rock `2`.

Hence:

`m_1 = 1 " kg"`
`m_2 = 2 " kg"`

We know that the force of gravity on the larger rock is twice the force of gravity on the smaller rock:

`F_2 = 2F_1`

Applying Newton's Law:

`m_2a_2 = 2m_1a_1`

`2a_2 = 2(1)a_1`

`cancel(2)a_2 = cancel(2)a_1`

`=>a_2 = a_1`

Hence, the accelerations are equal as expected.