A small explanation about misconception of measurements and units

This table explains common misconceptions about measurements versus facts about the measurements. 

Common Misconception	Fact
A light year is commonly understood as a unit of time	Light year is a unit of distance. One light year is the distance travelled by light through space in one year. 1 light year = 9.46x1015m
In measurement of all liquids 1kg=1 liter	The mass of liquid can be measured in kg while the volume of liquid can be measured in litre.

 System of units

The fundamental units of length, mass and time taken are from a system of units. For measuring various physical quantities following systems are commonly adopted.

Name of the system	Unit
	Length	Mass	Time
.    FPS	foot	pound	Second
.    CGS	centimetre	Gram	second
.    MKS	meter	kilogram	second

 Measurement of the volume of irregular solids can be made as follows.

S.No	To find the volume of	Description
1.	Solids insoluble in water, (a) But heavier than water	Take some water in a measuring jar and let its volume be v1 cm3. Immerse the solid completely in water using a string. The water level rises and the final level is v2 cm3. So, volume of solid = (V2-V1) cm3
	(b)Lighter than water	Let the volume of water be v1 cm3 when a sinker is immersed in it. Tie the solid to the sinker and immerse it into the water, now note the final level of water and let it be v2 cm3. The volume of solid = (v2-v1) cm3
2.	A single drop of water	1. Take a clean burette with water. Clamp it upright. 2. Remove any air bubbles formed. 3. Now allow water to trickle slowly drop by drop, and count the number of drops when the known volume of water has been drained out. 4. Average volume of a single drop = Volume of water drained out/number of drops
3.	The average volume of lead shots	1. Take a measuring jar with water of volume v1 cm3 2. Drop n number of lead shots into the water and note the final level of water as v2 cm3 3. Average volume of lead shot = (v2 – v1 /n) cm3