Tag: physical quantities

Questions Related to physical quantities

The unit kg $m^2s^{-2}$ is associated with

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Work

  2. Kinetic energy

  3. Potential energy

  4. All of these

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Correct Option: D
Explanation:

$kgm^2s^{-2}$ is the unit of energy. It's dimension is $[ML^2T^{-2}]$ All the quantities given in the option are different form of energy. So their units will be same. Then the unit $kgm^2s^{-2}$ is associated with all of the options.

Unit of power in S.I. system is

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Watt

  2. Calorie

  3. Newton

  4. Ergs

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Correct Option: A
Explanation:

Power is defined as the work done per unit time. So to get the SI unit of power :

$Power=\dfrac{Work}{Time}$

SI unit of Work $=$ Joules

SI unit of Time $=$ second

So S.I. unit of power $=\dfrac{Joule}{Second}=Watt$

The 'rad' is the correct unit used to report the measurement of

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. the rate of decay of radioactive source

  2. the ability of a beam of gamma ray photons to produce ions in a target

  3. the energy delivered by radiation to a target

  4. the biological effect of radiation

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Correct Option: D
Explanation:

Rad is the unit of absorbed dose of ionizing radiation. One rad is equal approximately to the absorbed dose delivered when soft tissue is exposed to one-roentgen of medium-voltage radiation. Thus this is the bilogical effect of radiation.

Which of the following statements below should be followed while using the symbol for a unit of a physical quantity?

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. The symbol named after scientist should have capital letter.

  2. They take plural forms.

  3. They can be written in full.

  4. They should be written only in the agreed symbols.

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Correct Option: A,C,D
Explanation:

1. They symbol named after scientist should have the capital letter, 

2. They can be written in full 
3. They should be written only in the agreed symbols be used while using the symbol for a unit of a physical quantity. 
4. They cannot take plural forms.

In CGS system, units of density is 

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. kg/m$^3$

  2. gm/m$^3$

  3. kg/c.c

  4. gm/c.c

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Correct Option: D
Explanation:

The gram per cubic centimetre is a unit of density in the CGS system, defined as mass in grams divided by volume in cubic centimetres.

Unit of heat in S. I. system

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Watt

  2. Newton/ Meter

  3. Ergs / Sec

  4. Joule

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Correct Option: D
Explanation:

Heat is a form of energy that flow from a hotter body to a colder one.

S.I. unit of heat: Joul, Joule is defined as the amount of energy exerted when a force of one newton is applied over a displacement of one meter.
Option D.

1 Kilocalorie $=$ ..................... joules.

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. $4000$

  2. $5000$

  3. $4200$

  4. None of these

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Correct Option: C
Explanation:

Calorie is defined as the amount of heat energy needed to raise the temperature of one gram of pure water by one degree Celsius. $1$ Kilocalorie are $1000$ calories, the amount of caloric energy needed to raise the mass of$1$ kg of pure water by $1^0C$. $1$ kilocalorie is $4200$ Joules.

Option C. 

Which of the following is not a characteristic of the standard unit?

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. It should be of convenient size.

  2. It should change with respect to space and time.

  3. It should not be perishable.

  4. It should be easily reproducible.

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Correct Option: B
Explanation:

Standard unit does not change with respect to time and space. Thus option B is correct.

In the SI system, the unit of temperature is:

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. Degree centigrade

  2. Kelvin

  3. Degree celsius

  4. Degree Fahrenheit

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Correct Option: B
Explanation:

The S.I. unit of temperature as per the International System of Units is Kelvin which is represented by the symbol $K$. The Kelvin scale is widely accepted or used in the field of science and engineering.

The dimensions of $\varepsilon _0\frac {d \Phi _E  }{  dt} $ is (where symbols has their usual meaning)

physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

  1. $[AT]$

  2. ${A}$

  3. $[ML^2T^{-2}]$

  4. $[ML^{-2}T^{-2}]$

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Correct Option: A