Pressure
1 Marks Question
 What is atmospheric pressure?
 The pressure exerted by the weight of air on the surface of the earth is called atmospheric pressure.
 Name two instruments which can be constructed on the basis of Pascal's Law.
 Two instruments which can be constructed on the basis of Pascal's Law are the hydraulic press, and hydraulic lift.
 What is upthrust?
 When a body is immersed in a liquid or gas completely or partially it experiences the resultant upward force which is called upthrust. Its SI unit is Newton.
 State the law of flotation.
 The Law of flotation states that when a body floats in a liquid it displaces the liquid whose weight is equal to its own weight.
 State the Archimedes principle.
 Archimedes principle states, "when a body is immersed partially or completely in a liquid, it experiences an upthrust which is equal to the weight of liquid displaced."
 Name two instruments that are based on the law of floatation.
 Hydrometer and ship are based on the law of floatation.
 State Pascal's law. Write the name of instrument based on pascal law.
 Pascal's law states that the pressure applied in an enclosed liquid is transmitted equally in all directions perpendicular to the surface. The name of the instrument based on pascal's law are hydraulic press, hydraulic brakes, jacks, hydraulic lift etc.
 Write two conditions when a substance float on liquid.

Two conditions when a substance float on liquid are:
 The density of object should be less than that of liquid.
 The weight of liquid displaced should be equal to its own weight.
 Define pressure.
 The perpendicular force applied on a unit area is called pressure. Its SI unit is N/m or pascal.
 Name the device based on pascal's law:
 The device based on pascal's law are: hydraulic press, hydraulic brakes, jacks, hydraulic lift etc.
 What is lactometer?
 Lactometer is a specially designed hydrometer which is used to measure the relative density of milk, that is; purity of milk.
 Mention any two factors which effect the upthrust.

Factors which effect the upthrust are listed below:
 Acceleration due to gravity  (g)
 Density of the liquid  (d)
 Volume of the liquid displaced  (V)
 On the basic of which principle is the hydrometer constructed?
 Hydrometer is constructed on the basic of Archimedes' principle.
 Write down the formula to find the relative density of an object.

The formula to find the relative density of an object is:
Relative density = density of substance / density of water at 4°C
It has no unit.  What is one pascal pressure?
 The pressure exerted on a surface area 1 m^{2} by the 1N force is called one pascal pressure.
 State law of flotation. Name a device based on this law and mention its use.
 Law of flotation states that, when a body floats in a liquid it displaces the liquid whose weight is equal to its own weight. Ships are based on this law which is used for transportation purpose in sea.
 On which principle does hydraulic brake based? State this principle.
 Hydraulic brake is based on pascal's law. It states that the pressure exerted at any point in an enclosed liquid is transmitted equally in all direction throughout the liquid.
 By which two properties of liquid is it used in hydraulic brakes?

Properties of liquid by which it used in hydraulic brakes are listed below:
 Nonhydroscopic.
 High boiling point and low freezing point.
 What is hydraulic press?
 Hydraulic press is the device which works under the principle of pascal's law of liquid pressure and converts small forces into larger force. It is used for compressing cottons, cardboard, for squeezing oil from seeds.