The Common Balance Viva Questions
(i) What is the principle of a physical balance?
Ans: It is form of lever of first order and works on the principle of moments.
(ii) What are the requisites of a good balance?
Ans: Truth, sensibility and stability
(iii) What is a true balance'?
Ans: A balance is true if the beam remains horizontal when the pans are empty or when they are equally loaded
(iv) What is meant by sensibility of a balance?
Ans: It is the mass required to change the resting point by one division
(v) What is the function of the plumb line in a balance?
Ans: We can level the balance with the help of the plumb line so that the beam rotates in a vertical plane
(vi) While weighing, the shutter must be closed. Why?
Ans: This is to avoid disturbance due to air current
(vii) Is it advisable to weigh a hot body?
Ans: No, with hot body convection currents are set up in air, which disturb the equilibrium.
(viii) What is the difference between mass and weight?
Ans: According to Newton's first law of motion mass is a measure of the inertia pos-sessed by the body which makes it resist any change in its state of rest or motion. It is also defined as the quantity of matter contained in it. Weight of a body is the force with which the earth attracts the body towards its centre
(ix) What are the S.I. unit of mass and weight?
Ans: Mass—kilogram; Weight—Newton
(x). Define mass and weight.
Mass of a body is the amount of matter contained in it. Weight an body is the force with which the earth attracts the body towards its centre.
(xi). What is the S.I. unit of mass?
kilogram (kg)
(xii). What is the S.I. unit of weight?
newton (N)
(xiii). Mention some differences of mass and weight.
i. Mass is a scalar quantity whereas weight is a vector quantity.
ii. Mass of a body is a constant whereas weight is not a constant. It is different at different places.
(xiv). How do you measure mass?
Mass is measured using a common balance.
(xv). How do you measure weight?
Weight is measured using a spring balance.
(xvi). What is the unit used for measuring mass of atom or subatomic particles?
Atomic mass unit
(xvii). What is meant by density of a substance?
It is the ratio of mass to the volume of a body.
(xviii). What is the standard value of density of water at 4° C?
Density of water = 1000 kg/m3
(xix). While weighing, you usually close the shutter of the balance. Why?
While weighing, we usually close the shutter of the balance in order to avoid air current.
(xx). Why are the knife-edges and plates made of agate?
To reduce friction
(xxi). Is it advisable to weigh a hot body?
No
(xxii). Why do you put standard masses in the right-hand pan and the body in the left hand pan?
Standard masses are put in the right hand pan for convenience. (Masses can be adjusted more frequently).
(xxiii). Define relative density.
Relative density is defined as the ratio of the density of a substance to the density of water at 4°C.
(xxiv). What is meant by the sensibility of the balance?
It is the mass required to change the resting point by 1 division.
(xxv). What are the requisites of a good balance?
Truth, Sensibility and Stability