Two rocks (call them S and T) are released at the same time from the same height and start from rest. Rock S has 20 times the mass of rock T. Which rock will fall faster if the only forces involved are each rock's mutual gravitational attraction with Earth?
a. Rock S
b. Rock T
c. Both rocks will fall at the same rate.
d. Not enough information is available to answer.

c. Both rocks will fall at the same rate.

Explanation:

An object that moves because of the action of gravity alone is said to be free falling.

All objects free fall at the same rate regardless of their mass.

So, even though Rock S has 20 times the mass of rock T, it would not affect their rate as according to Galileo, two bodies of different masses, dropped from the same height, will touch the floor at the same time in the absence of air resistance.

Therefore, on earth, two objects of different masses fall at the same rate.

be subject to a force andchange its motion

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s