Forces that act on objects by direct or indirect physical contact are called contact forces.
E.g. Applied or muscular forces and frictional force
Muscular Force:
The force is caused by the action of muscles in our body. The force resulting due to the action of muscles is known as the Muscular force.
It is the muscular force that enables us to perform all activities involving movement or bending of our body.
Lungs expand and contract while we inhale air during breathing.
Animals also make use of muscular force to carry out their physical activities and other tasks. Animals like bullocks, horses, donkeys and camels are used to perform various tasks for us.
Since muscular force can be applied only when it is in contact with an object, it is also called a contact force.
Frictional Force:
Friction is the resistance to motion experienced when two surfaces in contact move with respect to each other.
Whenever the surface of one body slides over that of another, each exerts a force on the other which opposes the motion of the body. This is called frictional force.
A ball rolling along the ground gradually slows down and finally comes to rest. When we stop pedaling a bicycle, it gradually slows down and finally comes to a stop. A car or a scooter also comes to rest once its engine is switched off.
The force of friction always objects and its direction is always opposite to the direction of motion. Since the force of friction arises due to contact between surfaces, it is also an example of a contact force.
