Take a bottle and pour any kind of drinkable juice in it. Now shut the bottle with a bottle cap and push it across the table. What did you just do when you pushed it across the table? Let us do another activity: now take a straw and sip the juice. Now while doing so, what’re you doing? In both the activities you applied both Force and Pressure.
When you pushed the bottle across the table you applied force and when you were sipping the juice through a straw you applied pressure. Isn’t it interesting how we use force and pressure in our daily lives? Let us study more about it below.
On a daily basis, we walk, we run, we play, we sit or stand. In all of these activities, we are changing the state of motion. We are bringing some object to rest or bringing it in motion. What is this called? What’re we actually doing? We’re actually applying ‘Force’ while bringing the object to rest or in motion. But what is a force? What are the effects of force?
You’re in your room, sitting and reading this. At this very moment, are you actually applying any force? If so, then what type of force are you applying? Now, take a bottle and push it across the table. Did you just apply force? What type of force did you apply? Pushing the bottle across the table comes under ‘Applied Forces’. Let us study more in-depth about the types of forces.
Forces can be divided into primarily into two types of forces:
Contact Forces
Non-contact Forces
Any types of forces that require being in contact with another object come under ‘Contact Force’. All mechanical forces are contact forces. Contact forces further divide into following types of forces:
Muscular Forces
Muscles functions to produce a resulting force which is known as ‘muscular force’. Muscular force exists only when it is in contact with an object. We apply muscular force during the basic day to day work of our life such as breathing, digestion, lifting a bucket, pulling or pushing some object. Muscular force comes in handy to simply our work.
Pressure is defined as the physical force exerted on an object. The force applied is perpendicular to the surface of objects per unit area. The basic formula for pressure is F/A (Force per unit area). Unit of pressure is Pascals (Pa). Types of Pressures are Absolute, Atmospheric, Differential, and Gauge Pressure. While sipping beverages from a straw, have you noticed that you actually suck the air out of the straw? While you sip the beverage, you’re actually applying ‘Pressure’.
The amount of force exerted (thrust) on a surface per unit area is defined as ‘Pressure’. It can also be defined as the ratio of the force to the area (over which the force is acting).
Pressure (P) = Thrust/ Area
The SI unit is ‘pascals (Pa)’. 1 Pa = 1N/m2
Example: It is easier to hammer a sharp pin than to hammer a blunt pin. This is because the area at the end of the sharp pin is smaller than the area at the end of a blunt pin. This leads to an increase in pressure leading to hammer the sharp pin easily.
Atmospheric Pressure
Absolute Pressure
Differential Pressure
Gauge Pressure
The earth’s atmospheric air is surrounded by a layer of gases and so this air surrounding the earth exerts a pressure known as the ‘atmospheric pressure’. Its value at sea level is 101325 Pa.
It is measured using a mercury barometer (hence atmospheric pressure is also known as barometric pressure), indicating the height of a column of mercury which exactly balances the weight of the column of atmosphere over the barometer. It can be expressed in several different systems of units such as millimeters (or inches) of mercury, pounds per square inch (psi), dynes per square centimeter, millibars (mb), standard atmospheres, or kilopascals.
The atmospheric pressure decreases near Earth’s surface, with height at a rate of about 3.5 millibars for every 30 meters (100 feet).