We use the method of dimensions to solve for the exponents a, b, and c.
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Identify Dimensions:
Period (T): [T] Pressure (P): Force/Area = [ML−1T−2] .
Density (D): Mass/Volume = [ML−3] . Surface Tension (S): Force/Length = [MT−2] .
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Equate Dimensions:
[T]=[P]a[D]b[S]c
[M0L0T1]=[ML−1T−2]a[ML−3]b[MT−2]c
[M0L0T1]=[Ma+b+cL−a−3bT−2a−2c]
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Solve System of Equations:
For Mass (M): a+b+c=0 (Eq. 1) For Length (L): −a−3b=0⇒a=−3b (Eq. 2)
- For Time (T): −2a−2c=1 (Eq. 3)
- Calculation:
Substitute a=−3b into Eq. 1: (−3b)+b+c=0⇒c=2b. Substitute a=−3b and c=2b into Eq. 3:
−2(−3b)−2(2b)=1
6b−4b=1⇒2b=1⇒b=1/2
Find a: a=−3(1/2)=−3/2. Find c: c=2(1/2)=1.
Therefore, a=−3/2,b=1/2,c=1.