Pressure
Why can camels still stand on sand without sinking despite their weight? Why don't we sink into the snow when we are skiing? That's because of pressure.
What is pressure? Pressure is the amount of force applied over an area.
Another way to view pressure is that pressure tells us how concentrated a force is. Here's the formula: Pressure = Force
Area
Pressure is very useful from gauges, hydraulics, barometers and more (explored later!) The thing we will explore in this article is pressure and surfaces.
Unit
The unit of pressure is Pascal (Pa) and it is equal to 1 N/m^2.
An apple in your hand exerts about 1000 Pa.
Different surfaces Most surfaces can only withstand a certain amount of pressure.
Which means once something exceeds that amount of pressure, the thing is gonna break. So how do you increase pressure? There are two ways - stop peeking and think about it first! The first way is to increase the force so whatever the area is the pressure would still be a large value. Here's the second way, which explains the concept of "sharp" objects:
Whatever the force is, if we decrease the area the force is applied to, we would be able to maximise the force! Don't understand? Here's an example: let's say we are exerting 10000N of force
with a needle with an area of 0.001m^2 with a tractor wheel with an area of 5m^2
Pressure = 10000/0.01 = 1000000 Pa 10000/5 = 20000 Pa As you can see, by varying the area, we can increase or decrease the amount of pressure exerted onto an object or a surface. This way, doctors can cut with scalpels with minimum force as the area of the blade is small, and tractors can move over mud without sinking because the weight is dispersed over a large area.
Exercise
A female friend of yours wants to go dancing and wants to try out her new pair of Stiletto shoes - Italian for dagger. They're basically high heels, and for this pair, each heel has an area of 1 cm^2. Your friend weighs 60 kg and the floor at the party can resist 5 MPa (million pascals) of pressure. Should she wear those shoes? This is an easy problem but let's tackle it step by step. First, find out the pressure the shoes exerts:
Pressure = Force/Area Force = 60 kg * 10 N = 600 N
(we are multiplying by ten to get the force because of something called weight)
Area: 1cm^2 = 0.00001 m^2
Pressure = 600N = 6000000 Pa
0.00001m^2
So those shoes will exert 6 MPa of pressure - as we can see, this exceeds the maximum amount of pressure the floor can withstand, which means the heels will damage the floor; so unless she's really rich or really generous, I don't think she should wear those shoes.
