Physics - Unit & Dimension Question with Solution | TestHub

PhysicsUnit & DimensionMiscellaneousEasy2 minPYQ_2020
PhysicsEasysingle choice

The speed of light c, gravitational constant G and Planck’s constant h are taken as fundamental units in a system. The dimensions of time in this new system should be:

Options:

Answer:
A
Solution:

Let time,   T∝ c X G Y h Z   ⇒T=k c X G Y h Z Taking dimensions on both sides  [ M 0 L 0 T 1 ]= [L T −1 ] X [ M −1 L 3 T −2 ] Y [M L 2 T −1 ] Z i.e.,  [ M 0 L 0 T 1 ]=[ M −Y+Z L X+3Y+2Z T −X−2Y−Z ] Equating powers of M, L, and T, on both sides, we get –  −Y+Z=0     ...(1)   X+3Y+2Z=0      ...(2)   −X−2Y−Z=1       ...(3) From equation (i)Adding (2) and (3)   Y+Z=1 or            2Y=1    ( ∵  Z=Y )   ∴Z=Y= 1 2       Putting these values in (2), we get –  X+ 3 2 +1=0  or  X= −5 2 Hence,   [T]=[ G 1 2   h 1 2   c −5 2 ]

Stream:NTA_ABHYAS_NEETSubject:PhysicsTopic:Unit & DimensionSubtopic:Miscellaneous
⏱ 2mℹ️ Source: PYQ_2020

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