# Is there force without pressure?

I know that when an object has been applied force to, this is called pressure, so if I apply some kind of force to a chair like push it forward or pull it forward that would be pressure, my question is that can there be force without pressure?

## 1 Answer

I'm not sure of your definition of pressure. The usual one in physics, given by wikipedia, is the amount of force acting per unit area, perpendicular to the surface.

Whenever you apply a force to something, if the force is distributed on the surface (meaning that the force you are applying can be described by many small forces perpendicular to the surface), you can define a pressure. Concretely, when you push a chair with your finger, the pressure will be something close to the total force you apply to the chair divided by the surface of your finger.

Many forces can't be described with the notion of pressure. For example, the weight is a force which is distributed on the volume of an object so you won't be able to understand this force with pressure.

• That's so confusing... Can you be more simply explaining pressure? sorry. I find it hard to understand Commented Jan 22, 2017 at 12:46
• Ok let me try to be less technical. I think that when you say pressure, you don't think about the physical definition of pressure. See wikipedia for this (link in previous answer). Then, take a ball in your hand and let it fall. A force is applied on the ball that makes it fall. Is it a pressure ? I don't think so. Commented Jan 22, 2017 at 12:54
• So when I pull a chair this is force. When I sit on chair this is pressure? correct? Commented Jan 22, 2017 at 13:12
• Somehow you are right, but it's not physically correct ;-). I suggest you to dig into what pressure is, the physical meaning and you will understand my concerns. Commented Jan 22, 2017 at 13:20
• So when the force of gravity is applied to an object(lets say ball) in the air it pushes it downwards, we consider the object as the surface and gravity as the force. So isn't this an overall pressure? then why can't we call it pressure? Commented Jan 22, 2017 at 13:23