Lesson 2: Pressure due to solids

You should now be familiar with the concept that pressure in solids depends on the surface area of the contact. If you apply a force to a small surface area the pressure will be greater than if you applied the same force to a larger surface area. Watch the YouTube video below which proves this concept, based on the formula:

Revision Monkey. (2021). Pressure in solids. (Standard YouTube licence)

Let's consolidate what was covered in the video by providing you with another example:

This object weighs 5 N. Let's calculate the pressure created when this object is placed with its largest base in contact with the table:

 
Now let's look at if the object which weighs 5N being placed on the table with its smallest surface area in contact:

Conclusion

0.208 N/cm² > 0.125 N/cm² therefore this proves that the smaller surface area exerts more pressure on an object than the larger surface area. 

In the above example we have illustrated the effect that the size of a surface area has on pressure. However, if the amount of applied force is increased i.e. F increases, then the amount of pressure exerted on the object will also increase.

Applications of pressure due to solids

To round off this topic, let's look at further practical applications of pressure due to solids:

• Screws, nails and drawing pins are designed with sharp points to increase their penetration ability
• Knives have sharp blades in order to enable them to cut through objects
• Porcupines have sharp quills in order to protect them from predators
• High heeled shoes can be problematic when walking on sand or grass. Flat shoes will not pose the same problem
• Railway sleepers are placed under the railway tracks to provide a larger surface area for the weight for the train
• Buildings are constructed with wide foundations in order to absorb the weight of the construction over a larger area

What other examples can you think of?