Tag: physics

Questions Related to physics

Which of the following is not used as SI prefixes:

physics dynamics - explaining motion system of unit summary of si units system of units

  1. Deca

  2. Kilo

  3. Femto

  4. Mica

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Correct Option: D
Explanation:

When 'Deca' is attached as a prefix to a unit, it means it is 10 times of that unit.  Kilo means thousand times of a unit.  Femto means of $ {10}^{-15} $ of a unit. Mica is not a prefix but a name of a specific material.

Which of the following is used as SI prefixes:

physics dynamics - explaining motion system of unit summary of si units system of units

  1. Femto

  2. Atto

  3. Zepto

  4. All of the above

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Correct Option: D
Explanation:

Here femto, atto and zepto, all are used as a prefix in the SI system.

In metric systme, $1 $ femtometer $=10^{-15}$ meter,  $1 $ attometer $=10^{-18}$ meter and $1 $ zeptometer $=10^{-21}$ meter

Which of the following is used as SI prefix:

physics dynamics - explaining motion system of unit summary of si units system of units

  1. Mega

  2. Hecto

  3. Tera

  4. Mara

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Correct Option: A,B,C
Explanation:

Mega, Hecto and Tera are used as SI prefix. Mega is used for $10^{6}$, Hecto for $10^2$ and Tera for $10^{12}$.

If the values of force and length are increased four times, then the unit of energy will be increase by:

physics dynamics - explaining motion system of unit summary of si units system of units

  1. 4 times

  2. 2 times

  3. 8 times

  4. 16 times

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Correct Option: D
Explanation:
The correct option is D
We have, $f=4[MLT^{-2}]$ and $d=4[L]$

$E=f\times d$

We know that Energy is equal to the product of force and distance.

Thus,
$=4[MLT^{-2}]\times4[L]$

$=16[ML^2T^{-2}]$

If both increased by 4times then the energy increased by $16\ times$

If unit of mass, length and time are tripled, then unit of energy becomes:

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $3$

  2. $\dfrac{1}{3}$

  3. $9$

  4. $\dfrac{1}{9}$

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Correct Option: A
Explanation:
Unit of Energy $kg\,m^2/s^2$

Unit of length $= m$ (metre)

Unit of mass $= kg$ (kilogram)

Unit of time $= s$ (second)


Thus unit of energy in terms of unit of mass, length and time is given by,

$Unit \,of\, Energy =\dfrac{(Unit\,of\,mass)\times(Unit\,of\,length)^2}{(Unit\,of\,time)^2}$

If the unit of mass, length and time are tripled the unit of energy will be,

$Unit \,of\, Energy =\dfrac{(3\times Unit\,of\,mass)\times(3\times Unit\,of\,length)^2}{(3\times Unit\,of\,time)^2}$

$Unit \,of\, Energy =3\times \dfrac{(Unit\,of\,mass)\times(Unit\,of\,length)^2}{(Unit\,of\,time)^2}$

$Unit\,of\,energy=3\times Unit\,of\,energy$

Therefore, if the unit of mass, length and time are tripled, the unit of energy will be, 3 times more than the original unit of energy.

If a thermometer reads freezing point of water at 20 degree Celsius and boiling point as 150 degree Celsius, how much thermometer can read when the actual temperature is 60 degree Celsius?

physics dynamics - explaining motion system of unit summary of si units system of units

  1. 98 degrees celsius

  2. 10 degree Celsius

  3. 40 degree Celsius

  4. 60 degree Celsius

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Correct Option: A

The unit of length, mass and energy are doubled.Which of the  following is /are correct?

physics dynamics - explaining motion system of unit summary of si units system of units

  1. unit of time is doubled

  2. unit of momentum is doubled

  3. unit of power is doubled

  4. Both (1) & (2)

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Correct Option: B

In the equation $\left( P+\dfrac { a }{ { V }^{ 2 } }  \right) \left( v-b \right) =RT,$ the SI unit of a is

physics dynamics - explaining motion system of unit summary of si units system of units

  1. N ${ m }^{ 2 }$

  2. ${ m }^{ 4 }$

  3. N${ m }^{ -3 }$

  4. ${ m }^{ -2 }$

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Correct Option: C

The melting point of pure ice is

physics dynamics - explaining motion system of unit summary of si units system of units

  1. $ 23.5^o C $

  2. $ 100^o C $

  3. 273.15 K

  4. 100 K

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Correct Option: C
Explanation:

The melting point of pure ice is $0^0C$. To convert temperature from degree Celsius to Kelvin, we add $273.15$.


So , $0^0C = (0+273)\,K = 273\,K$

Then, melting point of pure ice is $273.15\,K$.

If $10 ^ { 7 }$ erg is taken as unit of energy, $10 ^ { 5 }$ dyne as theunti of force, one second as unit of time, what is the unit of length? 

physics dynamics - explaining motion system of unit summary of si units system of units

  1. 1$m$

  2. 10$\mathrm { m }$

  3. 100$m$

  4. none

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Correct Option: B