2007-11-17 11:33:05 · 14 answers · asked by Jiovanni G 1 in Science & Mathematics ➔ Physics
Gravity.
2007-11-17 11:35:21 · answer #1 · answered by Emily S 1 · 0⤊ 0⤋
If the ball is at rest on a surface, there is the force of gravity mg and the force the surface exerts on the ball to balance that out.
It could also be at rest in another force field ( e.g. the demonstration of a fan keeping a ball seemingly at rest in the air where the gravitational force is balanced by the force of the air on the ball ( and Bernoulli forces keeping the ball IN the stream of air ). which balances out the gravitational force.
2007-11-17 11:40:19 · answer #2 · answered by LucaPacioli1492 7 · 0⤊ 0⤋
I think you're talking about inertia.
Read this wikipedia entry on Newton's laws for more info.
http://en.wikipedia.org/wiki/Newton's_laws_of_motion
I believe gravity, friction, air pressure, etc would, by definition, remove the "at rest" part of the equation. If a thing is being pulled down by gravity, it's no longer at rest, even if it appears so to us.
But don't just take my word for it. I'm no physicist, nor a science teacher.
Do you have a textbook to work from? If so, look up the publisher's website and see if it offers homework help. There may even be a URL (web address) on the cover or inside the book that you can use to find the tutorials that accompany the book. You can also try using a search engine to look up "free science homework help" and see what's available there.
Read up on it yourself to try for a better understanding. Good luck!
2007-11-17 11:38:29 · answer #3 · answered by Dinky 3 · 0⤊ 0⤋
There are TWO forces acting on the ball at rest.
The first force is gravity, which acts on all objects pulling it downwards. The second force is the normal force, which is exerting a force perpendicular to the contact surface. Otherwise, the ball would go right through the surface.
2007-11-17 11:50:24 · answer #4 · answered by Himitsu 3 · 0⤊ 0⤋
Two forces come into the picture
1) Its weight ie mass*acceleration due to gravity(m*g)
2)the reaction force of the earth to the weight of the body(magnitude equal to its weight but direction is perpendicular to the surface)
Since it is not in motion air resistance do not have an effect on it
2007-11-17 12:52:53 · answer #5 · answered by vidya r 2 · 0⤊ 0⤋
gravity from the earth pulling down.
contact force from the earth pushing up.
there is no friction because the ball is at rest.
2007-11-17 12:13:32 · answer #6 · answered by Anonymous · 0⤊ 0⤋
gravity! because gravity is what is keeping the ball at rest and keeping it in its same position
2007-11-17 11:35:45 · answer #7 · answered by xCottonx3Candyx 2 · 0⤊ 0⤋
0 force and gravity would pull it down making it completely still
2007-11-17 11:35:58 · answer #8 · answered by Jimmy A 1 · 0⤊ 0⤋
Inertia, for one. There's gravity, too. Centrifugal force also.
2007-11-17 11:41:58 · answer #9 · answered by sameetwo 1 · 0⤊ 0⤋
Gravity and air pressure.
2007-11-17 11:37:20 · answer #10 · answered by jim s 3 · 0⤊ 0⤋