Question

Three rocks, each of varying mass and volume, are released from a window at the same time. The window is at height h above the ground. Which rock, if any, will strike the ground at the fastest speed? Assume that air resistance affects the rocks equally.
A. all three rocks will achieve the same speed

B. the largest rock

C. the most massive rock

D. the densest rock

Answer 1

Under the assumption that the three rocks are dropped from the same height, they will hit the ground at the same speed. The gravity of Earth is virtually the same for any object that is small compared to the size of the Earth. The acceleration will change with the distance from the Earth, but this change is so small for the range of heights we work with (consider the range of heights from sea level to the tip of Mount Everest) that we can take the average value and assume it to be constant. This constant value of acceleration due to Earth's gravity is 9.80665m/s²

Because the objects fall under the same constant acceleration, they will hit the ground at the same speed.