Force meaning in Physics Force definition Class 9

The word “force” is used for the first time in Newton’s first law. But the interesting thing is, what do we mean by the word ‘force’ is still not described. If it was another book other than physics then instead of using the word ‘application of force’ if we use the word ‘application of energy’ then the meaning of the sentence will not be changed significantly. Since it is a book of physics, hence we cannot use the word ‘energy’ here. In physics, the word ‘energy’ is a completely different quantity. Here we have to actually use the term ‘force’. But what is meant by force? Still now we have not given the definition of force.

Actually Newton’s first law of motion can be the definition of force. Force is that quantity the application of which a stationary object start move and a body moving, with a uniform velocity change its velocity. From Newton’s first law we can understand, what is force.

Definition of Force:

What that works on a stationary body to create or tends to create motion, or that which works on a motion body to change the motion of the body or tries to increase its velocity is called force.

Or, a force is that which acting on a body at rest produces or tends to produce motion or acting on a moving body changes or tends to change its state of motion.

When you use force in your daily life for different purposes, you may realize that for the application of some forces it is necessary to come in contact with the object (e.g. to lift heavy objects with the help of a crane, to push anything or coming to rest of moving objects due to friction). Whereas you may have noticed that for the application of some other forces, it is not necessary to come into contact with the object (falling of anything downwards due to gravitational force, attraction by magnets). So we can divide forces into two types, contact forces and non contact forces. But you definitely understood that the region we assumed to touch, but at that region the molecules, atoms and their revolving electrons of each other do not create force by direct touch rather one is working with the other by their electromagnetic forces. In other words we can say, if we go to the atomic scale, then all the forces are non contact in nature. One atom attracts or repulses another atom at a distance; they need not touch practically.

Reference: NCTB