STD VIII – PHYSICAL QUANTITIES AND MEASUREMENT (Online)

Measurement

Physical Quantities and Measurements.

Density

Density is defined as its mass per unit volume. It is, essentially, a measurement of how tightly matter is crammed together. 

Determination of density of a regular solid

First measure the mass M of the given regular solid by using a beam balance

Now find the volume V of the regular solid by using the formula,

Volume of cube = (one side)3

Volume of cuboid = length * breadth * height

Volume of sphere = 4π(radius)3/3

Volume of cylinder = π(radius)2(height)

Knowing mass and volume find the density by using the given formula,

Density = M/V

Vessels for measuring volume

Eureka Can

Measuring Cylinder

Determination of density of a liquid using density bottle

 A density bottle is a specially designed bottle which is used to determine the density of a liquid.

Concepts of Floatation

Floating and sinking

Students commonly believe that:

Heavy objects sink and light objects float regardless of their size, shape or the type of material used to make them

Law of floatation

When a body floats in a liquid, the weight of the liquid displaced by its immersed part is equal to the total weight of the body. This is the law of floatation.