Units and Measurement - Class IX

The fundamental units are the units of the fundamental quantities, as defined by the International System of Units. They are not dependent upon any other units, and all other units are derived from them. There are seven basic fundamental quantities: Length, mass, time, electric current, amount of substance, luminous intensity & temperature. The quantities which are derived with the help of these basic physical quantities are called derived quantities. They are density, volume, pressure, force, etc.

Angstrom $(\dot A)$ unit of length used chiefly in measuring wavelengths of light, equal to $10^{-10}$ metre, or $0.1$ nanometer.  It is used to express wavelengths of visible light, ultraviolet (UV) light, X rays, and gamma rays.

Parsec is the largest unit of length. It is usaed to measure the space distances.

Gravitational force is the force exerted by earth on any body which attracts to body towards earth. It is same as any other force.  The gravitational unit of force in the metric system is $kg,wt$.

Solar luminosity is defined as the total amount of energy emitted by a star per unit time. Luminous flux and intensity relate to human perception of light, not total energy emission.

Power is defined as work divided by time, so its units are joules/second. Scientists have another name for this unit, too. It's the watt, named after James Watt, the Scottish inventor who helped develop the steam engine that powered the Industrial Revolution. In the SI system, the watt is defined as:

The SI unit of weight is Newton  (N). Option C

Among the given units metre is not a unit of British system whereas all other units belong to this system.

Torque$={ M }^{ 1 }{ L }^{ 2 }{ T }^{ -2 }$

Gas equation,
$PV=nRT$

SI unit of amplitude of oscillation is metre  $(m)$

Angstrom $(\dot A)$ unit of length used chiefly in measuring wavelengths of light, equal to $10^{-10}$ metre, or $0.1$ nanometer.  It is used to express wavelengths of visible light, ultraviolet (UV) light, X rays, and gamma rays.

SI unit of mass is kilogram i.e.  $Kg$.
Thus the above statement is false.

A unit is said to be a standard unit of does not change with respect to space and time.

Surface Tension$ (T) =\dfrac{ Force}{Length}$  . . . . . (1)

Since, $Force = Mass \times Acceleration$

And, $Acceleration = \dfrac{velocity}{ time}= [L T^{-2}]$

$\therefore $ The dimensional formula of force $= M^1L^1T^{-2}$ . . . . (2)

On substituting equation (2) in equation (1) we get,

Surface Tension $(T) = \dfrac{Force}{  Length}$

Or, $T=\dfrac{[M^1L^1T^{-2}]}{[L^{1}]}=M^1T^{-2}$ 

Therefore, surface tension is dimensionally represented as $[M^1T^{-2}]$

Dimension of force $=M^1L^1T^{-2}$

So the dimension of force and surface tension are different.

$F = A\ cosBx + C\ sinDt$

 The answer is $0.0075006157584566$. We assume you are converting between and pascal. You can view more details on each measurement unit: mm Hg or pascal The SI derived unit for pressure is the pascal. $1 mm Hg =133.322387415 \ pascal$.

MKS unit of force is $kg \ m/s^2$ which is also expressed as Newton. Thus the above statement is true.

Given pressure $\displaystyle = \frac{Force}{Area}$
$\therefore$ MKS unit of pressure $\displaystyle = \frac{S.I.  unit \ of    force}{S.I.  unit \ of \ area} = \frac{kg  m  s^{-2}}{m^2}$
$\displaystyle = \frac{kg.m}{m^2 . s^2} = \frac{kg}{m.s^2}$
$\therefore$ MKS unit of pressure $= kg m^{-1} s^{-2}$
SI unit of pressure is pascal.

The C.G.S. unit of speed is $ cm/s$.

In S.I system (standard international system), the units of mass,length and time are same,as that of M.K.S system. However , it is an enlarged system encompassing all fundamental units.

In MKS system,M stands for metre (length),K stands for kilogram(mass) and S stands for seconds(time).

Planck's constant, symbolized h, relates the energy in one quantum (photon) of electromagnetic radiation to the frequency of that radiation.  In the centimeter-gram-second (CGS) or small-unit metric system, it is equal to approximately $6.626176\times 10^{-27},$Erg Second.