Question

Write the name of the instrument used to measure the mass of an object and state its principle.

Answer 1

Hint: The mass of an object is measured with the help of a physical balance. It has two ends to keep unknown mass on one end and some known masses on the other. When the balance rests in the horizontal axis, both the masses on both the ends are equal and this way we find the mass of an object.

Complete answer:
We know what mass of a body is. Mass of a body is the amount of matter within the volume of the body.
The mass of an unknown body is measured by an instrument called as physical balance. It consists of a beam that is hinged at its midpoint. This acts as a lever with both the arms of equal lengths.

The unknown body is placed on one end of the beam and a body of known mass is placed at the other end of the beam. When the lever rests in the horizontal axis, we say that the body of known mass balanced the unknown mass. This happens when the known mass is equal to the unknown mass.
Hence, we find the unknown mass by placing different bodies of known masses until the lever is balanced.
This instrument works on the principle of zero torque. When the masses on both the ends are equal, the gravitational force on both the ends are equal and both the forces are at equal distances from the hinged point. Therefore, the torques generated by each force cancel each other and thus the net torque on the beam is zero and it rests in the horizontal position.

Note:
Other than the physical balance, we have other instruments to measure the mass of an object. One of these instruments is a weighing machine. Another instrument is spring balance. Both the instruments work with the help of the gravitational force.