Physics Forces Question?

Question

In physics we were told that gravity pulls up down and that a chair for instance pulls up and that the forces balance each other out buy how can a chair have a force i find this a little confusing. Can any1 help?

Answer 1

i think what you are talking about is what is called a normal force. when you are sitting in a chair it holds you lets say 2 feet off the ground. gravity wants to pull your body all the way to the ground, but the chair is holding you at a constant distance, and therefore must be creating a force exactlly opposite and equal to the force of gravity acting on your body. the normal force exerted on your body by the chair is proportional to your body weight:
Fnormal(Newtons)=(-)Fgrav(N)=G(9.81 m/s^2) * Mass of object (kg)

Answer 2

While your question is worded in a confusing manner, I will try best to explain.

Gravity accelerates any mass down towards the center of the Earth. This is also represented as a force, as F = mass*acceleration = mg

An object sitting on the ground will not move down, however gravity still acts upon it. Thus, to counteract the force of gravity (which is required for an equilibrium "static" condition in which the chair is not moving), it is noted that there is an equal and opposite force that pushes up on the chair to counteract the force of gravity. This force would be supplied by the floor the chair is sitting on.

In the same manner, if you were sitting on the chair, you would experience both a force downward due to gravity, but also a force upward from the chair. Thus, the two forces cancel out as they are in opposite directions, and you do not move up or down.

Answer 3

Gravity is the attraction between two objects. It is related to their mass and the distance between them. If a tennis ball and a 250 kg person were floating in zero gravity 5 m apart, both would be pulled together but because of the mass differential, the person would attract the ball faster than the ball would attract the person. The same happens for your chair on earth. Because of the extreme difference in mass, the chair is pulled to and held firmly against the earth. If the chair were suspended above the ground it would exert a minuscule, almost unmeasurable attraction on the earth.

Answer 4

Newton's 3rd law states when one object exerts a force on another object, and equal and opposite force is exerted from the second object to the first.

For your scenario, basically a chair sitting on the floor. Gravity (9.8N) is being exerted on the chair causing the mass of the chair to have a weight, which in turn is exerted on the floor. The floor the chair is sitting on is exerting an equivalent amount of force on the chair, holding it up. Since net forces have to equal zero for neither objects to move, everything is stationary Make sense?

Answer 5

The chair isn't doing any pulling.

Gravity from the earth is pulling the chair down.

The chair is being held up by the floor (which is called the Normal force).

Since the chair is not accelerating (changing its speed), we have that the normal force and weight are related by

N = mg

where m = mass, g = acceleration due to gravity, and m*g = weight.

Answer 6

Any object has a physical attraction to another object. Take the moon for example It is atracted to the earth or it would not be revolving around it, and the earth also has a physical atraction towards the sun because it is revolving around it. The chair for instance is being forced up by the ground. The chair itself doesn't have a force it's self it is forced by the ground.

Answer 7

the force the chair exerts is its weight
which is essentially gravity.
since the chair has a mass and it has an acceleration (gravity).. it exerts a force.
now since the chair is not moving, it must mean that there is another force cancelling that one out...
so the ground is exerting an equal but opposite focr upward againt the chair.