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What are contact forces and non-contact forces?

Class 8 ScienceNCERT chapter: Exploring Forcesइसे हिंदी में पढ़ें

Exam-ready answer

Forces that act only when two objects are in contact are called contact forces, for example muscular force and frictional force. Forces that act on an object without touching it are called non-contact forces, for example magnetic force, electrostatic force and gravitational force. A magnet pulling an iron pin from a distance shows a non-contact force.

Explanation

A force is a push or a pull on an object. Some forces need the objects to touch each other. When we lift a bag, push a cart or kick a ball, our muscles apply force through contact. This is muscular force. When a ball rolling on the ground slows down and stops, the force of friction between the ball and the ground acts against its motion. Both are contact forces.

Some forces act even when there is a gap between the objects. A magnet pulls an iron pin from a short distance and pushes away the like pole of another magnet. This is magnetic force. A plastic comb rubbed on dry hair attracts small bits of paper without touching them. This is electrostatic force, caused by charges produced by rubbing.

The most common non-contact force is gravitational force. The Earth pulls every object towards itself, so a fruit falls from a tree and a ball thrown up comes back down. The weight of an object is the force with which the Earth pulls it. Every object attracts every other object, but this pull is noticeable only when one of them is very large, like the Earth.

Points to remember

  1. Force: a push or a pull on an object.
  2. Contact forces act only through touch: muscular force and frictional force.
  3. Non-contact forces act from a distance: magnetic, electrostatic and gravitational force.
  4. Friction always opposes the motion between two surfaces in contact.
  5. Weight is the gravitational force with which the Earth pulls an object.

Exam tip

Answer with a two-column table: contact forces (muscular, friction) and non-contact forces (magnetic, electrostatic, gravitational), giving one everyday example for each.

Questions students also ask

Is friction a contact force?
Yes. Friction acts only between two surfaces that touch each other, such as a ball and the ground or shoes and the floor. It opposes the motion of one surface over the other.
Why is gravitational force called a non-contact force?
The Earth pulls objects towards itself without touching them. A fruit falling from a tree or a ball coming down after being thrown up moves because of this pull acting across empty space.
What is electrostatic force?
Electrostatic force is the force exerted by an object carrying electric charge on another object. A comb rubbed on dry hair gets charged and attracts small bits of paper without touching them.

Chapter labels help you find the topic in your textbook. Check your own edition: chapter names and order can change. These are Know.it explanations, not official NCERT solutions.