TYPES OF FORCES
There are five common types of force which we notice in our everyday life. These are:
1. Muscular force,
2. Frictional force (or Friction),
3. Magnetic force,
4. Electrostatic force, and
5. Gravitational force.
All type of forces can be divided into main groups : Contact forces and Non contact forces. Please note that the state of one object ‘physically touching’ another object is known as ‘contact’. So, when one object physically touches another object, they are said to be ‘in contact’. The force can act on the object with or without contact with the object. We now now describe contact forces and non contact forces in detail, one by one.
A force which can be exerted by an object on another object only through ‘physical touching’ is called a contact force. The examples of contact forces are :
1. Muscular force, and
2. Frictional force (or Frictional).
Let us now discuss muscular force and frictional force in detail, one by one.
Suppose a book is lying on a table. It takes some power to bring this book up from the table. When we lift this book from the table by hand, the force is exerted by the muscles of our arm. Similarly, when we kick a football, the force is exerted by the muscles of our leg. The force exerted by the body muscles is called muscle strength. Both, human beings and animals exert muscular force to do work. Humans exert powerful power for carrying out various daily activities such as walking, running, jumping, climbing, lifting, pushing, pulling, kicking, kicking, stretching, squeezing, twisting and pressing objects. A boy pushing a cart on a road, a person drawing water from a well are all examples of the use of muscular force. It is muscle strength that allows us to perform all activities involving movement or bending of the body part. Push the muscles of food through the digestive tract. The expansion and contraction of lungs when we inhale and exhale air during breathing, also involves muscular force. And the beating of heart also take place by the muscular force produced by cardiac muscles.
A Force can Change the Shape and Size of an Object
When we press the dough with a rolling pin, we apply force. So, we can say that the shape of dough changes on applying force. When the potter converts it into pots of different shapes and sizes, the shape of the kneaded wet clay changes. This happens because the potter exerts a force on the kneaded wet clay. The shape of a toothpaste tube (or on ointment tube) changes when we squeeze it because we apply force while squeezing it. When we hammer a piece of aluminium metal, its shape changes and an aluminium sheet is formed. This change in change in shape occurs because we apply force while shape hammering. When we sit on a sofa with springs, then the springs of the sofa get compresses them. Similarly, the shape of sponge, tomato, balloon or tennis ball changes on pressing. And the shape and size of a rubber band changes on stretching. The shape and size of a balloon changes when it is filled with air (or water) because the weight of air (or water) exerts force on the walls of the balloon from inside. Form these examples, we conclude that a force can change the shape and size of an object. We will now discuss the various types of forces.