Question

the force of gravity on a 2-kg rock is twice as great as that on a 1-kg rock. Why then doesnt the heavier rock fall faster?

Answer 1

Newton's Law:

F=ma

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

Hence:

m1=1 kg
m2=2 kg

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

F2=2F1

Applying Newton's Law:

m2a2=2m1a1

2a2=2(1)a1

2a2=2a1

⇒a2=a1

Hence, the accelerations are equal as expected.