Contact And Non-Contact Forces

To move anything we need force. The force causes motion or change in motion.

There are different forces that can cause motion.

But all the forces are classified into two types based on whether they have "contact" or not.

They are contact forces and non-contact forces. Now let's study them in detail.

Contact forces

These type of forces can have effect only when they have contact.

Tension in a string is a contact force because without tying it on both sides is tension cannot have an effect.

Spring force is also a kind of tension force. So it is also a contact force.

Muscular force is a contact force. This is also a type of tension force because the muscle fibres are also strings.

The frictional force on the ground is a contact force because without the contact between the ground there is no friction.

Friction always acts parallel to the surface.

Normal force is a force that acts on a body when it is in contact toa surface.

Normal force always acts perpendicular to the surface.

The combined effect of the friction and normal force acts as shown.

It is called the reaction force. The reaction force is also a contact force.

The friction offered by liquids is called the viscous force, it is also a contact force.

viscous force is very less compared to the friction that's what we use oil as lubricants in machines.

The reaction force offered by liquids is called buoyant force. It is also a contact force.

If the buoyant force is more than the weight of the body then the body floats on water otherwise it will sink.

Now let's see about non-conact forces.

Non-Contact forces.

These forces can interact with other objects without any object.

Gravitational force is the best example of a non-contact force.

This force is responsible for the objects to fall back on to the ground.

The moon rotates around the earth and the earth rotates around the sun due to gravity.

Magnetic force is a non-contact force. It is the force between two magnets or magnet and magnetic materials.

The electrostatic force is a non-contact force. This is the force of attraction or repulsion between charges.

Eg: take a comb and brush your hair a few times and bring it near pieces of paper. We can see the pieces getting attracted to the comb.

There are some other non-contact forces like strong nuclear forces and week nuclear forces. We will study them in higher classes.

Revision

Force is something that causes a change in motion. There are two types of forces.

Contact forces need contact between objects to interact.

Contact force examples are Frictional force, Normal force, Reaction force, Tension force, Muscular force, Spring force, Viscous force and Buoyant force.

Non-Contact force doesn't need any contact between the objects to interact.

Examples of non-contact forces are Gravitational force, Magnetic force, Electrostatic force, Strong nuclear and week nuclear forces.

The end