Class 9 Science Chapter 10 Gravitation
“Thrust is force acting perpendicular to the surface.”
Consider a box kept on table. Box exerts force on table. Therefore, direction of force is perpendicular. Hence, one can say that the box exerts thrust on the surface of table.
Effect of thrust
Effect of Thrust
It can be demonstrated by very good example. When you stand on sand, feet goes deep with in the sand. Feet has smaller surface area, and weight of body is the thrust applied on the sand. If you lay down on sand, body does not go deep into the sand. This is because, body has larger surface area. In both the cases, weight of body remains same, but applied thrust is more in first case and less in second case. Hence, it can be concluded that, if body or object has smaller area, thrust applied is more otherwise it is less (i.e.vice versa) .
Pressure
Pressure is the thrust applied per unit area.
Force exerted on smaller area exerts more pressure whereas, large area exerts less pressure. If you observe a nail and a knife, nail is pointed at one end. It has smaller area hence it apply more force. Knife has one end sharper because of same reason. Sharp end has small area, hence, force exerted is more therefore, pressure exerted is more. Pressure is given by Thrust / Area.
It is measured in unit N/m2 or Pa i.e in Pascals.
Pressure in fluids
Pressure can be exerted not only by solids but also by fluids (Liquid and solid). Moreover, Fluids apply pressure on the walls of container as well as in all direction.
Keywords: Pressure, Pressure in liquids, Gravitation.
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