Measurement of Mass (Weight)
In everyday life we usually compare the mass of different objects. We can compare the mass of two things by lifting or holding the objects with our hands and find out which object is heavier or lighter. But everything we can lift or hold and this type of measurement are not accurate, they are just rough estimates.
Example: If we hold pencil on one hand and book on other hand, we can easily say that book is heavier than the pencil.
Measuring the mass of an object is also known as weighing the object. We use different weighing scales or weighing machines to weigh objects.
In case of balance scale, when two objects weigh the equal, the two pans of the weighing scales are said to be balanced and stay at the equal level and when one object heavy and other is lighter, the pan with the heavier object goes down and the pan with the lighter object goes up.
We need to use suitable units to measure the masses of objects. The standard unit of mass is the gram. We write gram as ‘g’.
1000 grams put together make a bigger unit called kilogram. Kilogram is written as ‘kg’ in short.
1kg = 1000g
Or
1000g = 1kg
We measure lighter objects in grams whereas heavier objects in kilograms.
Word Problem
Example 1: Three friends weigh 28 kg, 30 kg and 32 kg. Find their total weight.
Solution:
Example 2: Ria’s mom bought 3 kg grapes, 2 kg oranges, 2 kg apples and put them in her bag. Find the total weight of the fruits in her bag.
Solution: