FORCE AND PRESSURE
- A push or pull exerted by an object on another is a force.
- Force arises due to the interaction between at least two objects.
- Force has both Magnitude and Direction
- Force applied on an object in the same direction add to one another.
- If the two forces act in the opposite direction on an object, the net force acting on it is the difference between the two forces.
- In general, more than one force may be acting on an object at any given point.
- However, a force acting on an object is always the mean net force acting on it.
Two friends pushing a heavy load (a) in the same direction and (b) in the opposite direction
- A Force can Change the State of Motion
- A change in the speed of an object or the direction of its motion or both implies a change in its state of motion.
- Force acting on an object may bring a change in its state of motion or a change in its shape.
Ex: A rubber band suspended from a hook/nail fixed on a wall.
By hanging a weight or by pulling its free end.
Types of Forces:
Contact Forces: The forces act on a body when the source of force is in actual contact with the body.
- (i) Muscular Force: The force exerted by the muscles of the body.
- (ii) Mechanical Force: The force produced by a machine.
- (iii) Frictional Force: The force that opposes the motion of an object.
Non-Contact Forces: Forces which do not involve physical contact between two bodies on which they act.
- (i) Magnetic Force: A magnet exerts a non-contact force on objects made of iron, steel, cobalt or nickel.
- (ii) Electrostatic Force: The force which result due to repulsion of similar charges or attraction of opposite charges.
- (iii) Gravitational Forces: The force that exists between any two masses because of their mass.
- Thrust: The force that acts on a surface in a direction perpendicular to it, is known as thrust.
- Pressure: The force acting on per unit area, applied to an object in the direction perpendicular to the surface is called pressure.
- Liquids exert pressure on the walls of the container in which they are kept.
- Gases exert pressure in all directions.
- Atmospheric Pressure: The pressure exerted by atmospheric air around us is known as atmospheric pressure.