$(a)$. Define frictional force (or friction).
$(b)$. Explain why frictional force is said to be a contact force.
$(c)$. Explain why magnetic force is said to be a non-contact force.

(a). A frictional force is a force between two surfaces that are in contact and that move or slide against each other.

Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.

There are several types of friction: Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Frictional forces exist in fluids i.e., liquids and gases also.

(b). A friction force is said to be a contact force as it acts between the surfaces of the two objects. So, friction force can't act until the surfaces of two objects are in contact with each other.

(c). A magnetic force acts between the two bodies by the imaginary magnetic lines of the magnet which are emanated from the north pole (N) to the South Pole(S). It is observed that a magnetic material like iron can be influenced by a magnet even without contact. So a magnetic force is a non-contact force.

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Updated on: 10-Oct-2022

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