Any interaction that can result in a change in the motion of an object if left unopposed is called a force. Forces are responsible for many phenomena. For example, the earth orbits the sun as a result of the centripetal force which is provided by gravity (learn about other centripetal force examples here). Forces can be broadly classified into two types – contact forces and non-contact forces.
A force that can only be applied when contact with the object is established is known as a contact force. All mechanical forces are considered to be contact forces. Some important types of contact forces are listed below.
- Muscular forces: the forces produced by the muscular functions in animals are called muscular forces. These forces can be used to push, pull, lift, throw, and perform many other tasks. Even the process of breathing and digestion involve the use of muscular force.
- Frictional force: when one surface attempts to move over another one, a resisting force arises between the surfaces. This force is known as the force of friction. The lighting of a matchstick is a result of frictional force.
The pressure exerted by a gas on the walls of its container is also a type of contact force that results from the collision of the gas particles with the container walls. The ideal gas equation provides a relation between the pressure, volume, number of moles of the gas, and the temperature.
Non-contact forces do not require any direct contact with the object to exert a force on it. Examples of non-contact forces include gravitational forces, electrostatic forces, and magnetic forces. For example, when a stone is thrown up into the air, it eventually falls back down to the Earth. This is because the Earth does not require to be in direct contact with the stone to exert a gravitational force on it.
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