Question

A beam balance is used to measure the ______ of a body.
(A). Weight
(B). Mass
(C). Force
(D). Shape

Answer 1

Hint: It is a device which works on the principle of moments and compares the forces. Principle of moments states that when a body is balanced, then the sum of moment at a point must be zero, where the moment is the product of force and the distance from the pivoted point. The most used two-pan beam balance is a lever.

Complete step by step answer:
The beam balance is a device used for the determination of the mass of a body under gravitation.
Beam balance is used for high precision measurements like masses up to 250g, it consists of a pair of scale pans one at each end of a rigid beam. The pans are suspended through stirrups and there is wooden baseboard which is provided with three levelling screws where two among them are of adjustable heights and through these the baseboard is levelled horizontally.
When two masses are placed in pans it compares the weights of the object. Weights are directly proportional to masses if they are weighed in the same place.

Let us consider object A having gravitational mass ${{m}_{1}}$ and B having gravitational mass ${{m}_{2}}$which is standard and known.
Now keep ${{m}_{1}}$ in one pan and go on add standard mass ${{m}_{2}}$ till they become horizontal and align in a straight line
Then we get, weight of A= weight of B
i.e., ${{m}_{1}}g={{m}_{2}}g$
where g is acceleration due to gravity, by cancelling it we get,
${{m}_{1}}={{m}_{2}}$
so the unknown mass ${{m}_{1}}$is equal to standard mass ${{m}_{2}}$.
Thus, mass is measured in beam balance comparing force(weight).
Correct option is B.

Note: Students may get confused between weight and mass and select option a, which is wrong-
Mass is a measure of the amount of matter in a body denoted by the symbol ‘m’ is constant and independent of place and position.
Whereas weight is the force acting on mass due to acceleration due to gravity denoted by $W=mg$ it depends on ‘g’ so when you move to places where g varies weight also changes according to g.
Here by comparing weight we measure mass as we know acceleration due to gravity.