Question Details

Which of the following pairs of physical quantities does not have same dimensional formula?

Options

A

Work and torque.

B

Angular momentum and Planck’s constant.

C

Tension and surface tension.

D

Impulse and linear momentum.

Correct Answer :

Tension and surface tension.

Solution :

The correct option is Tension and surface tension.

To understand why this is the correct answer, we can analyze the dimensional formulas of each pair of physical quantities given in the options.

1. Work and Torque:
Work done is defined as force multiplied by displacement:
Work=Force×Displacement
The dimensional formula of force is [MLT-2] and displacement is [L]. Therefore, the dimensional formula of work is:
[Work]=[MLT-2]×[L]=[ML2T-2]
Torque is defined as the cross product of position vector and force:
Torque=Force×Perpendicular Distance
Thus, the dimensional formula of torque is:
[Torque]=[MLT-2]×[L]=[ML2T-2]
Since both have the dimensional formula [ML2T-2], they have the same dimensions.

2. Angular Momentum and Planck's Constant:
Angular momentum (L) is given by:
L=mvr
where m is mass [M], v is velocity [LT-1], and r is distance [L]. The dimensional formula is:
[L]=[M]×[LT-1]×[L]=[ML2T-1]
Planck's constant (h) is related to energy (E) and frequency (ν) by E = hν:
h=Eν
The dimensional formula of energy is [ML2T-2] and frequency is [T-1]. Thus, the dimensional formula of Planck's constant is:
[h]=[ML2T-2][T-1]=[ML2T-1]
Since both have the dimensional formula [ML2T-1], they have the same dimensions.

3. Tension and Surface Tension:
Tension is a pulling force exerted by a string, cable, or chain. Since it is a force, its dimensional formula is:
[Tension]=[MLT-2]
Surface tension is defined as force per unit length:
Surface Tension=ForceLength
Thus, the dimensional formula of surface tension is:
[Surface Tension]=[MLT-2][L]=[MT-2]
Comparing the two, [MLT-2] is not equal to [MT-2]. Therefore, tension and surface tension do not have the same dimensional formula.

4. Impulse and Linear Momentum:
Impulse is defined as force multiplied by time duration:
Impulse=Force×Time
Thus, the dimensional formula of impulse is:
[Impulse]=[MLT-2]×[T]=[MLT-1]
Linear momentum is defined as mass multiplied by velocity:
Momentum=Mass×Velocity
Thus, the dimensional formula of linear momentum is:
[Momentum]=[M]×[LT-1]=[MLT-1]
Since both have the dimensional formula [MLT-1], they have the same dimensions.

Consequently, the only pair that does not share the same dimensions is Tension and surface tension.

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