Measurements and Experimentation – Exercise 1(A) — Very Short Answer Type

Ans: Measurement is the process of comparison of the given quantity with the known standard quantity of the same nature.

Ans: Unit is the quantity of a constant magnitude which is used to measure the magnitudes of other quantities of the same nature.

Ans: A physical quantity is expressed in terms of the following parameters:
The unit in which the quantity is being measured, and
The numerical value which expresses, how many times the above selected unit is contained in the given quantity.

Thus, the magnitude of physical quantity is expressed as : Physical quantity = (numerical value) x (unit)

Ans: The three fundamental quantities are —
Mass
Length
Time

Ans: The S.I. unit of Luminous intensity is candela (cd).

Ans: One parsec is the distance from where the semi major axis of orbit of earth (1 A.U.) subtends an angle of one second.

Ans: A fundamental unit is that which is independent of any other unit or which can neither be changed nor can be related to any other fundamental unit.

Example – Units of mass, length, time, temperature, current etc.

Ans: Derived units are those which depend on the fundamental units or which can be expressed in terms of fundamental units.

Example: For the measurement of area, we need to measure length and breadth in the unit of length and then express area in a unit which is length x length or (length)²

Ans: The standard metre is defined in terms of speed of light, according to which, one metre is the distance travelled by light in 1/299,792,458 of a second in air (or vacuum).

Ans: Relation between nanometer (nm) and Angstrom (Å) is expressed as:
1 nanometer = 10 Å

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Ans: A leap year is the year in which the month of February is of 29 days.
1 Leap year = 366 days
Every fourth year (i.e., the year divisible by 4) has one day extra in the month of february (i.e., February has 29 days) and so it is the leap year.

Ans: Yes the statement is true.
We know that, if any year is divisible by 4, then it is a leap year and in a leap year, February has 29 days. As, the year 2024 is divisible by 4, so it will have 29 days in February.

Ans: A lunar month is the time of one lunar cycle, i.e., it is the amount of time it takes for the Moon to complete one orbit around the Earth and it is nearly equal to 29.5 days.

Ans: 1 nano second = 10^-9 s
1 µs = 10^-6 s
1 mean solar day = 86400 s
1 year = 3.15 x 10⁷ s

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