Applications of Viscosity:

• The viscosity of liquids plays a major role in the selection of lubricating materials for various machines. Heavy machines require lubricant having high value of viscosity whereas light machines require low viscous oil. For example, a cycle requires oil of higher viscosity for lubrication as compared to a watch.
• The quality of fountain pen ink depends largely on its viscosity.
• The normal circulation of blood through arteries and veins depends on the viscosity of blood.
• The shape of the aircraft, the ship and the car is streamlined to minimise the effects of viscosity.

Till now, you learnt some characteristic properties of fluids. You must have noted that these properties of fluids have a variety of applications and they also enable us to explain some of the day-to-day observations. Further, the numerous ways in which we have been able to use solid materials is truly amazing. Be it the sewing needle or the ship or the satellite, we need solids. The question is: How do we decide which solid material is appropriate for making a particular object such as a sewing needle or a ship? Well, the choice of material is decided on the basis of some of characteristic properties of solids. One such property is known as elasticity. Elasticity plays an important role in selection of materials for construction of buildings, bridges, machines etc. You will now learn elasticity of solids.