A push or pull on an object is called force. A force acting on a particular area produces pressure. Not only solids, but also liquids and gases exert pressure; the hydraulic lift and the hydraulic brake work due to liquid pressure. This lesson also covers surface tension, viscosity and friction.
1. Force
Opening a door, kicking a football or striking a carrom coin needs an external agency. This external agency is called force. Force can set an object at rest into motion, bring a moving object to rest, and even change the shape and size of certain objects.
Definition: Force is an external agency which changes or tends to change the state of rest or the state of uniform motion of a body, or the direction of a moving body, or the shape of a body.
- Force is a vector quantity – it has magnitude and direction.
- Its unit is the newton (N); the SI unit of force is newton.
- Force acts only when two or more objects interact with one another.