4.17. Acceleration Due to Gravity http://www.ck12.org
Mass and Acceleration Due to Gravity
What if you were to drop a bowling ball and a soccer ball at the same time from the same distance above the ground?
The bowling ball has greater mass than the basketball, so the pull of gravity on it is greater. Would it fall to the
ground faster? No, the bowling ball and basketball would reach the ground at the same time. The reason? The
more massive bowling ball is also harder to move because of its greater mass, so it ends up moving at the same
acceleration as the soccer ball. This is true of all falling objects. They all accelerate at the same rate due to gravity,
unless air resistance affects one object more than another. For example, a falling leaf is slowed down by air resistance
more than a falling acorn because of the leaf’s greater surface area. You can simulate the effect of air resistance on
acceleration due to gravity by doing the interactive animation at this URL: http://www.science-animations.com/su
pport-files/freefall.swf
Q: If a leaf and an acorn were to fall to the ground in the absence of air (that is, in a vacuum), how would this affect
their acceleration due to gravity?
A: They would both accelerate at the same rate and reach the ground at the same time.
Summary
- When gravity pulls objects toward the ground, it always causes them to accelerate at a rate of 9.8 m/s^2.
- Regardless of differences in mass, all objects accelerate at the same rate due to gravity unless air resistance
affects one more than another.
Vocabulary
- acceleration: Measure of the change in velocity of a moving object.
- gravity: As traditionally defined, force of attraction between things that have mass.
Explore More
Watch the video at the following URL. Based on the teens interviewed in the video, identify two common miscon-
ceptions about gravity, mass, and acceleration due to gravity. Then explain why each misconception is false.
http://www.youtube.com/watch?v=_mCC-68LyZM
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/117722Review
- Why do objects fall faster the longer they fall toward Earth?
- What is the rate of acceleration due to gravity?
- How does mass affect acceleration due to gravity?