FORCE AND PRESSURE
When an object is either pushed or pulled is known as a force. Motion, generated in an object, is because of an action of a force. The applied force makes the table move in a given direction. The strength of a force is commonly expressed by its magnitude.
Force also has direction; likewise, if the magnitude or direction changes, it directly affects the force. If the force is applied in the direction opposite to the direction of motion, then it results in a decrease in the speed of the object.
- If an object is in motion, then external force may change in the state or the direction of motion of that object.
- The state of motion of an object is explained by its speed and direction of motion.
- The state of the ‘rest’ of an object is considered to be zero speed, as
- An object cannot move by itself.
- An object cannot change its speed by itself.
- An object cannot change its direction by itself.
- An object cannot change by itself.
- A force may make an object move from rest.
- A force may change the speed of a moving object.
- A force may change the direction of a moving object.
- A force may change the shape of an object.
- The force caused by the action of muscles is known as the muscular force.
- Some force that decreases the speed of a moving object, is known as ‘friction.’
E.g. moving the wheel on road; once the source of force stops working, then the wheel stops because of friction.
The force applied by a charged body on another charged or uncharged body is known as ‘electrostatic force.’
Objects or things fall toward the earth, as the earth pulls it towards itself this force is known as the force of gravity or gravity.
The force of gravity is applicable to all objects. In fact, every object in this universe, irrespective of its size and shape, exerts some force on every other object. It happens only because of the ‘gravitational force.’
Pressure
- The force, applied on a unit area of a surface is known as pressure (Pressure = force/area on which it acts).
- If the area is smaller, then the pressure on a surface would be greater; e.g. this is the reason that the area of one end of a nail is pointed (to exert sufficient pressure) and another end is bigger (as shown in the image given below).
- This envelope of air is known as the atmosphere extends up to many kilometers above the surface of the earth
- The pressure exerted by the air is known as atmospheric pressure.
- The pressure inside our bodies is exactly equal to the atmospheric pressure and annuls the pressure acting from outside (see the image given below).
There can be a major difference between force and pressure, even though both are physics entities. In order to understand the difference, we need to understand the definition and its application. Force is the push and pull action resulting in the change of motion and direction, whereas pressure is the physical force per unit area.
Difference Between Force and Pressure
Force is the effect caused by the interaction of two objects which tries to change the state of the object. The pressure is the force acting on an object in the perpendicular direction to the surface of the object which results in the spreading of force over a certain area.
This could be similar to the difference between stress and pressure. Therefore, if force is applied over a large area, then pressure is said to be low and if the same force is applied to a small area, then the resulting pressure is said to be high.
Difference Between Force and Pressure | |
Force | Pressure |
The push and pull action results in the acceleration of the object | Force acting upon a certain area and acted upon something perpendicular to its surface |
Its unit is Newton and is represented by N | Its unit is Pascal and is represented as Pa |
The instrument to measure force is called a dynamometer | An instrument to measure pressure is called a manometer |
Force is a vector quantity which means it also has a direction | The pressure is a scalar quantity which means it does not have a direction |
Force can be acted upon on the face, edges, side or vertices of the object | Pressure only acts on the surface or face of the object |
The velocity of an object can be changed with the application of force in one direction | Pressure on the object won’t change the direction of the object. |
• Force: a push or a pull on an object is called force. Force may impart motion to an object it is applied to an object in the same direction add to one.
• Magnitude: the strength of a force is usually expressed by its magnitude
• State of motion: The state of motion of an object is described by its speed and direction of motion.
• Muscular Force: The force resulting due to the action of muscles is known as the muscular force.
• Contact Force: The force which is applied when it is in the contact with the object.
• Non-contact force: The force exerted on an object without touching it is known as noncontact force.
• Gravitational force: the attractive force of earth which acts upon all the objects is called the force of gravity or gravitational force.
• Pressure: The force acting on a unit area of a surface is called pressure. It acts perpendicular to the surface on which pressure is exerted.
• Pressure= force/area on which it acts. The lesser the area, the greater is the force.
• Both liquids and gases exert pressure on the wall of their containers.
• Atmospheric pressure: The pressure on the atmospheric air is known as atmospheric pressure. This weight of air column over a unit 1cm2