Question Details

To determine the Young's modulus of a wire, the formula is Y = (F/A).(L/Δl); where L= length, A= area of cross- section of the wire, ΔL = Change in length of the wire when stretched with a force F. The conversion factor to change it from CGS to MKS system is

Options

A

1

B

10

C

0.1

D

0.01

Correct Answer :

0.1

Solution :

To find the conversion factor for Young's modulus from the CGS system to the MKS system, we first need to determine its dimensions and units in both systems.

Young's modulus is given by the formula:
Y=FA·LΔl

Let's analyze the units of the quantities involved:
- Force (F) has dimensions of [MLT-2].
- Area of cross-section (A) has dimensions of [L2].
- Length (L) and change in length (Δl) both have dimensions of length [L], so the ratio L��l is dimensionless.

Therefore, the dimensional formula of Young's modulus (Y) is:
[Y]=[MLT-2][L2]=[ML-1T-2]

Now, let's write the units of Young's modulus in both systems:
- In the CGS system, the unit is g·cm-1·s-2 (or dyne/cm²).
- In the MKS system, the unit is kg·m-1·s-2 (or N/m2).

Let's convert 1 CGS unit of Young's modulus to the MKS unit:
1 CGS unit=1 g·cm-1·s-2

Substitute the conversion values for mass and length:
- 1 g=10-3 kg
- 1 cm=10-2 m

This gives:
1 CGS unit=(10-3 kg)·(10-2 m)-1·s-2

Simplify the exponents:
1 CGS unit=10-3·102 kg·m-1·s-2

1 CGS unit=10-1 MKS unit=0.1 MKS unit

Thus, the conversion factor to change Young's modulus from the CGS system to the MKS system is 0.1.

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