Back to: Basic Science Primary 3
Welcome to class.
Mass is the measurement of how much matter is contained in an object. The mass of an object is the amount of particles in an object. It is the same everywhere, i.e. the mass on earth is the same as the mass on moon. The mass does not depend on size, i.e. a large object may be lighter than object that is much smaller.
The mass of the two objects can be compared to judge how heavy or light they are. For example, a small stone is heavier than a bigger wool.
When an object has more mass than the other, then it is said to be heavier.
INSTRUMENTS FOR MEASURING MASS
The mass of objects can be measured using different measuring instruments such as chemical balance, kitchen scale, bathroom scale, beam balance, unequal arm balance, etc.
Mass of an object can also be measured using a uniform wooden lever balance. This is achieved by comparing the unknown mass of object with a standard one (known mass). The center of the lever balance is placed on a fulcrum and the object with unknown mass will be placed on end of the lever while the object with a standard mass will be placed on the other side (both at the same distance from the ends). The mass of the standard object will be varied until balances the mass of the unknown object. Therefore, the mass of the unknown object is equal to the standard masses that counter- balanced it at the other end.
If the first car weighs 1kg, and the mass of the second car weighs 1kg, then, we say the level balance is equal.
But if the two masses are not equal, the heavier will push the level balance down and the lighter one will go up.
METRIC UNITS OF MASS
The standard unit of mass in metric system is gram (ng). the metric units if mass are kilogram (kg) and tonne (tn). Gram (g) is used to measure wight of light objects while tonne is used to measure very heavy objects. It should be noted that the units can be converted from one value to the other, such as:
1miligram (mg)= 0.001gram
1 centigram (cg)= 0.01gram
1 decigram (dg) = 0.1 gram
1 kilogram (kg) = 1000gram
1 tonne (tn)= 1,000,000 gram
EVALUATION
- What is mass?
- List any four instruments that can be used to measure the mass of objects
- The standard unit of mass is ———(a) km (b) m (c) g (d) kg
- Which of the following is mass measuring instruments (a) ruler (b) chemical balance (c) watch (d) clock
- List the two metric units of mass
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