Question Details

From the dimensional consideration, which of the following equation is correct

Options

A

T = 2π√(R³/GM)

B

T = 2π√(GM/R³)

C

T = 2π√(GM/R²)

D

T = 2π√(R²/GM)

Correct Answer :

T = 2π√(R³/GM)

Solution :

The correct option is T = 2π√(R³/GM).

To determine the correct formula using dimensional analysis, let us analyze the dimensions of each variable involved in the equation:
1. Time period, T has the dimension of time:
[T]=M0L0T1

2. Radius, R has the dimension of length:
[R]=L

3. Mass, M has the dimension of mass:
[M]=M

4. Universal Gravitational Constant, G can be derived from Newton's Law of Gravitation, F=Gm1m2r2:
[G]=[F][r2][m1][m2]=(MLT-2)(L2)M2=M-1L3T-2

Now, let us find the dimensions of the term GM:
[GM]=(M-1L3T-2)(M)=L3T-2

Next, let us check the dimensions of the expression on the right-hand side of the correct option, R3GM (noting that the constant 2π is dimensionless):
[R3GM]=(L3L3T-2)12=(T2)12=T

Since the dimensions of the left-hand side (T) match the dimensions of the right-hand side (T), the equation T=2πR3GM is dimensionally correct.

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