Question

If there are only four forces in nature, what are contact forces?

Answer 1

Answer:

A contact force is any force that requires contact to occur.Contact forces are ubiquitous and are responsible for most visible interactions between macroscopic collections of matter

Explanation:

let me give you a example:- kicking a ball or pushing a desk across a room are some of the everyday examples where contact forces are at work.

Answer 2

Some of the most important types of force are as follows: 1. Frictional force 2. Magnetic force 3. Electrostatic force 4. Gravitational force.

Frictional force:

You have learnt that a force is required to stop the movement of a body in motion. Then why does a swing not continue to move forever once you have given it a push? And why does a ball not roll endlessly once you have kicked it, even if no force is applied to stop it?This is because when (the surface of) one body moves over another, frictional force acts in a direction opposite to that of the motion. Frictional force always opposes motion, trying to stop the movement of one surface over another. However, how great the frictional force is depends on the nature of the two surfaces in contact.

Magnetic force:

Things made of iron are attracted by a magnet. The force with which a magnet attracts such things is called magnetic force, and the phenomenon is called magnetism. You must have noticed that a magnet does not have to be in contact with something made of iron in order to attract it. Unlike muscular force and frictional force, magnetic force can act from a distance.

3. Electrostatic force:

If you run a comb through your hair (provided it is dry) a few times and then hold the comb over small pieces of paper, they will get drawn to the comb. The force which acts on the pieces of paper is called electrostatic force. This is another type of force that can act from a distance. You will learn more about it in another chapter.

Gravitational force:

You know that everything on or near the earth is attracted towards it by the force of gravity. This is what makes a ball come down when you kick it upwards. Had there been no force of gravity, the ball would fly right away. The moon too pulls things near it with its own force of gravity. And so do all the other planets, the sun and all the stars. In fact, any two bodies in this universe attract each other by a force called gravitational force.

This law is called Newton’s law of gravitation in honour of Sir Isaac Newton, the English physicist and mathematician who discovered it. You may wonder why you do not feel your school bus or your classmates attract you with the force of gravitation.

The problem is that gravitational force depends on the masses of the two bodies concerned. And unless one of the bodies is very massive, it cannot be felt. This also explains why the earth’s force of gravitation is much greater than that of the moon. It is because the earth’s mass is much greater than that of the moon.