Does Force Acting at an Angle Contribute to Pressure on a Surface?

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Discussion Overview

The discussion centers around the question of whether a force acting at an angle contributes to pressure on a surface. Participants explore various scenarios involving forces applied perpendicular and parallel to surfaces, as well as the implications of pulling versus pushing forces.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants argue that a force acting at an angle does not exert pressure on a surface, with the exception of a force applied at 90 degrees to the surface.
  • Others clarify that any force with a component perpendicular to the surface will exert pressure proportional to that component, while components parallel to the surface may not contribute to pressure.
  • A question is raised about the effect of a pulling force on pressure, with some suggesting that if the force is capable of pushing or pulling at the surface, the perpendicular component will always contribute to pressure.
  • Participants discuss a scenario involving two blocks, one being pushed down and the other being pulled up, leading to questions about how pressure is calculated in each case.
  • There is a suggestion that if the pulling force exceeds atmospheric pressure, the resultant pressure could be zero, indicating that the force only partially contributes to pressure in that situation.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the effects of forces acting at angles on pressure. Multiple competing views remain regarding the contributions of different force components and the implications of pulling versus pushing forces.

Contextual Notes

Participants express uncertainty regarding specific scenarios, such as the conditions under which pulling forces may contribute to pressure and the definitions of pressure in different contexts (e.g., atmospheric pressure).

Puneeth423
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"Force acting at an angle doesn't exert pressure on a surface". Is this statement correct or wrong?
 
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it is generaly wrong. The only angle which wouldn;t make pressure is 90 degrees
 
xAxis said:
it is generaly wrong. The only angle which wouldn;t make pressure is 90 degrees

90 degrees with the surface?
 
90 degrees as in parallel to the surface. Any force that has a component perpendicular to the surface will exert pressure on the surface proportional to that component. The other components of the force may not contribute to the pressure in general.
 
Any force that has a component perpendicular to the surface will exert pressure on the surface proportional to that component.

What if the force is applied acting in a direction away from the surface?
 
then it is a pull rather than a push...
 
That wasn't the answer to my question, so let me rephrase it.

If the force is a pull, does it exert pressure Sometimes?, Always?, Never?
 
Last edited:
Well I am still ignorant of the situation you are referring to, but if the force is capable of pushing or pulling at the surface, then any component of the force perpendicular to the surface will contribute to pressure. Always. If you are referring to pressure of the atmospheric type, then there can be no "pulling", only pushing. So the angle would need to direct the force toward the surface.
 
Let us suppose there are two identical blocks sitting on the table.

So there is atmospheric pressure Pa acting on the top surface (area A) of each block.

Now suppose we push down onto the top surface of one block with a force F, via say a push rod.

then the total pressue on the top surface of the block is now

Pa + F/A

If we attach a sting to the top surface of the other block and pull up with a force F, that is insufficient to lift the block off the table,

What is now the pressure on the top surface of this block?
 
  • #10
Pressure on the top surface would be equal to the pressure on the bottom surface. For the first block the Pa + F/A is the pressure required on the bottom surface to lift the block. For the block with the string it should be Pa - F/A.
 
  • #11
So what happens when F/A > Pa ?
 
  • #12
pressure will be zero and the resultant force will lift the block.
 
  • #13
OK got you. the force only partially contributes to pressure in that case...The surplus does not :)
 
Last edited:

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