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Units And Measurement

Question
CBSEENPH11016618

A gas bubble from an explosion under water, oscillates with period T proportional to padbEc, where p is pressure, d is density and E is energy of an explosion. Find the value of a, b and c.  

Solution

Given, time period is proportional to straight T space alpha space straight p to the power of straight a straight d to the power of straight b space straight E to the power of straight c
Equating both sides of above equation dimensionally, we get
open square brackets straight M to the power of 0 straight L to the power of 0 straight T to the power of 1 close square brackets space equals open square brackets straight M to the power of 1 straight L to the power of negative 1 end exponent straight T to the power of negative 2 end exponent close square brackets to the power of straight a open square brackets straight M to the power of 1 straight L to the power of negative 3 end exponent straight T to the power of 0 close square brackets to the power of straight b open square brackets straight M to the power of 1 straight L squared straight T squared close square brackets to the power of straight c space

space open square brackets straight M to the power of 0 straight L to the power of 0 straight T to the power of 1 close square brackets space equals space open square brackets straight M to the power of straight a plus straight b plus straight c end exponent straight L to the power of negative straight a minus 3 straight b plus 2 straight c end exponent straight T to the power of negative 2 straight a minus 2 straight c end exponent close square brackets


Now, omparing the dimensions of M, L and T on both sides, we get
                   a + b + c = 0                      ....(1)
              - a - 3b + 2c = 0                      ....(2)
                      - 2a - 2c = 0                     ....(3)
Solving (1), (2) and (3), we get
              straight a equals negative 5 over 6 comma space straight b equals 1 half space and space straight c space equals 1 third