# Q & A: How does gravity affect acceleration?

Most recent answer: 10/22/2007
Q:
How does gravity affect acceleration?
- Shareef Amer (age 11)
Villa park IL
A:
Shareef -

Great question! And the answer is that, in a sense, gravity /is/ acceleration! You've probably heard of the "force of gravity," and you may have heard of the equation "F=ma." What this equation means is that the force on an object is the same as the mass of the object multiplied by how much it's being accelerated. The thing about gravity is that it has its own number for the "how much it's being accelerated" part, and that number is the same pretty much anywhere on a planet. For gravity on the Earth, that number is about 9.81 (m/s^2).

Since that doesn't change anywhere on Earth, the only thing that changes the force of gravity (as long as you're on Earth) is the mass of the object (which is a lot like how much it weighs). For example, if you were to drop two balls off of the top of a building at the same time, you'd see that they both accelerate exactly the same way, no matter how much either one weighs!

The thing that will change that number (for the acceleration of gravity) is how big the planet is that you're standing on. On the moon, for example, the acceleration of gravity (and the force of gravity) are about 1/6 of what they are on the Earth. So you would actually fall slower if you jumped on the moon than on the Earth. This is because the moon is much smaller than the Earth. But on a bigger planet than Earth, the acceleration of gravity would be bigger, and you'd fall faster.