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CBSE NOTES ⇒ Class 8th ⇒ Science ⇒ Chapter 11. Force and Pressure

Chapter 11. Force and Pressure


Force and Pressure:

Pressure: The force acting on a unit area of a surface is called pressure.

Pressure can also be defined as the ratio of the force exerted on a surface to the area on which the force is acting.

S.I Unit of Pressure is pascal (N/m2). 

Atmosphere: Envelop of air is known as the atmosphere.

Atmospheric Pressure: The pressure exerted by this air is known as atmospheric pressure.

Using broad straps in shoulder bag to reduce pressure: 

Broad straps reduce pressure on back. If the strap will be thin the value of pressure will be raised as per unit area of surface gets reduced.

Smaller area gives larger pressure for the same force: The area of the pointed end of the nail is much smaller than that of its head. The same force, therefore, produces a pressure sufficient to push the pointed end of the nail into the wooden plank.

Thin tip of nail experiences larger pressure applying same force on nail by hammer while broad tip of nail experience smaller force on applying same force. See the figure below. 

All liquids and gases exert pressure on the wall of their containers in which they kept. 

Vaccum Pressure: Pressure due to produced by absence of air is called vaccum pressure. 

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