Question:
I was wondering if I held a baseball and then a small
moon both 10000 feet high and dropped them would they close the gap
between themselves and and the earth in equal time. I guess what I'm
really asking is, do objects of different sizes really fall at precisely
32 feet per second squared? I ask because I read that all objects have an
attraction to each other.
Replies:
All objects with mass attract each other by gravity. The rate at which they
accelerate toward each other is NOT universally 32 ft/s^2. That's just the
acceleration experienced by a relatively light (compared to the earth)
object at the earth's surface. In fact, the attraction between two objects
depends on the masses of the objects divided by the square of the distance
between their centers of mass. So, if you move far enough away from the
surface of the earth, your gravitational acceleration toward the earth will
diminish.
So, in answer to the first part of the question, the speed at which your
tennis ball and moon approach each other will depend on their masses and
their separation. Chances are that it WON'T be the same rate at which they
fall toward the earth.
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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