Units And Measurement

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Question
CBSEENPH11020782

Dimensions of resistance in an electrical circuit, in terms of the dimension of mass M, of length L, of time T and of current I, would be:

  • [ML2T-3I-1]

  • [ML2T-2]

  • [ML2T-1I-1]

  • [ML2T-3I-2]

Solution

D.

[ML2T-3I-2]

Resistance 
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Question
CBSEENPH11020525

If energy (E), velocity (v) and time (T) are chosen  as the fundamental quantities, the dimensional formula of surface tension will be

  • [Ev-2T-1]

  • [Ev-1T-2]

  • [Ev-2T-2]

  • [E-2v-1T-3]

Solution

C.

[Ev-2T-2]

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Question
CBSEENPH11020562

If force (F), velocity (v) and time (T) are taken as fundamental units, then the dimensions of mass are

  • [FvT-1]

  • [FvT-2]

  • [Fv-1T-1]

  • [Fv-1T]

Solution

D.

[Fv-1T]

We know that,
F = ma
That is,
F = mv/t
straight m space equals space Ft over straight v
So, left square bracket straight M right square bracket space equals space fraction numerator left square bracket straight F right square bracket left square bracket straight T right square bracket over denominator left square bracket straight V right square bracket end fraction space equals space left square bracket space Fv to the power of negative 1 end exponent straight T right square bracket

Question
CBSEENPH11020717

If the dimensions of a physical quantity are given by Ma Lb Tc, the physical quantity will be 

  • pressure if a = 1, b = -1, c= 2

  • velocity if a = 1, b = 1, c = -2

  • acceleration if a = 1, b = 1, c =-2

  • force if a = 0, b = -1, c =- 2

Solution

A.

pressure if a = 1, b = -1, c= 2

Dimensions of velocity = [ M0L1T-1]
Here, a = 0, b =1, c = -1
Dimension of acceleration = [ M0L1T-2]
Dimension of force = [ M1L1T-2]
Dimension of pressure = [M1L-1T-2
The physical quantity is pressure.

Question
CBSEENPH11020741

If the error in the measurement of radius of sphere is 2%, then the error in the determination of volume of the sphere will be

  • 4%

  • 6%

  • 8%

  • 2%

Solution

B.

6%

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