Measuring Pressure on a Concrete Table

• Kevin Cheung
In summary, the conversation discusses the concept of measuring surface pressure on a concrete table with a small mass placed on it. The participants consider the force diagram and the contact area between the mass and the table, as well as the pressure difference between different points. They also discuss the idea of infinite pressure and the materials that could withstand it. The conversation concludes with a consideration of the distribution of pressure on a square solid.
Kevin Cheung
Homework Statement
To find the pressure difference between two points on the same surface
Relevant Equations
P=F/A
Hi guys, I am not doing homework, it is just suddenly brainstormed this question.

What if I place a very small mass like 10kg on the center of a concrete 10m*10m flat table supported by the ground, then how to measure the surface pressure acting on the center and right on the edge? Or the pressure difference between two particular points?

Pressure(center)=(10*9.8)/(?)
Pressure(edge)=(10*9.8)/(10*10)

It should be not correct, but how to measure the pressure at the particular point?

Kevin Cheung said:
... how to measure the surface pressure acting on the center and right on the edge?
Draw a force diagram showing exactly what you have in mind.

phinds said:
Draw a force diagram showing exactly what you have in mind.
It is just very simple, we can imagine it is not a "table" but a square solid.

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What is the contact area between the mass and the table?

Gordianus said:
What is the contact area between the mass and the table?
That is the tricky point, the weight is just like a point source, we could only have the information of dimension (the center to edge, the size of the table).

Kevin Cheung said:
That is the tricky point, the weight is just like a point source, we could only have the information of dimension (the center to edge, the size of the table).
If the table is rigid, it really doesn't matter whether the force is a point source or spread evenly across the whole area, now does it?

Kevin Cheung
Kevin Cheung said:
how to measure the pressure at the particular point?
The pressure of the ball at any point where the ball is not making contact is zero.

The pressure of an ideal ball on an ideal surface at the one and only point where contact is made would be infinite.

Kevin Cheung
jbriggs444 said:
The pressure of the ball at any point where the ball is not making contact is zero.

The pressure of an ideal ball on an ideal surface at the one and only point where contact is made would be infinite.
I get the point of the pressure of the contact point would be large as infinite, but could we tell the pressure difference between the contact point and the point away from it?

Kevin Cheung said:
I get the point of the pressure of the contact point would be large as infinite, but could we tell the pressure difference between the contact point and the point away from it?
Do you know of any materials that could withstand infinite pressure?

phinds said:
If the table is rigid, it really doesn't matter whether the force is a point source or spread evenly across the whole area, now does it?
Yes, assume it is rigid. I thought there are the same pressure on the two points before, but it seems wrong after considering the force is acting like a point.

phinds said:
Do you know of any materials that could withstand infinite pressure?
No, so it should only be very high pressure.

Kevin Cheung said:
It is just very simple, we can imagine it is not a "table" but a square solid.
I'm unsure what you are asking. If you mean the distribution of the pressure the square exerts on the ground below it, it depends on the moduli of rigidity. If the square is much more rigid than the ground the peak pressure may be towards the edge; at the opposite extreme, it will be at the middle (or wherever the point mass is).

1. How is pressure measured on a concrete table?

Pressure on a concrete table is typically measured using a device called a pressure sensor. This sensor is placed on the surface of the concrete and is able to detect the amount of force being applied to it.

2. What units are used to measure pressure on a concrete table?

The most common units used to measure pressure on a concrete table are pounds per square inch (psi) and kilopascals (kPa). However, other units such as bars or atmospheres may also be used.

3. What factors can affect the pressure measurement on a concrete table?

There are several factors that can affect the pressure measurement on a concrete table. These include the weight and distribution of the object being placed on the table, the surface area of the object, and the condition and type of concrete used in the table.

4. How accurate are pressure measurements on a concrete table?

The accuracy of pressure measurements on a concrete table can vary depending on the quality and calibration of the pressure sensor used. However, in general, pressure measurements on a concrete table can be quite accurate with modern technology.

5. Are there any safety precautions to consider when measuring pressure on a concrete table?

Yes, it is important to take proper safety precautions when measuring pressure on a concrete table. This may include wearing appropriate protective gear, ensuring the table is stable and able to support the weight, and following manufacturer's instructions for the pressure sensor being used.

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