Sponsor Area

Mechanical Properties Of Fluids

Question
CBSEENPH11020321

Water is flowing continuously from a tap having an internal diameter 8 × 10-3 m. The water velocity as it leaves the tap is 0.4 ms-1. The diameter of the water stream at a distance 2 × 10-1 m below the tap is close
to:

  • 7.5 x 10-3 m

  • 9.6x 10-3 m

  • 3.6x 10-3 m

  • 5.0x 10-3 m

Solution

C.

3.6x 10-3 m

From Bernoulli's theorem
ρgh space equals space 1 half straight rho left parenthesis straight v subscript 2 superscript 2 minus straight v subscript 1 superscript 2 right parenthesis
gh space equals space 1 half straight v subscript 1 superscript 2 space open parentheses open parentheses straight v subscript 2 over straight v subscript 1 close parentheses minus 1 close parentheses space left parenthesis therefore straight A subscript 1 straight v subscript 1 space equals straight A subscript 2 straight v subscript 2 right parenthesis
rightwards double arrow space space open parentheses straight A subscript 1 over straight A subscript 2 close parentheses squared space equals space 1 space plus space fraction numerator 2 hg over denominator straight v subscript 1 superscript 2 end fraction
rightwards double arrow open parentheses straight D subscript 1 over straight D subscript 2 close parentheses to the power of 4 space equals space 1 space plus space fraction numerator 2 gh over denominator straight v subscript 1 superscript 2 end fraction
rightwards double arrow space straight D subscript 2 space equals space straight D subscript 1 over open parentheses 1 plus begin display style fraction numerator 2 gh over denominator straight v subscript 1 superscript 2 end fraction end style close parentheses to the power of 1 divided by 4 end exponent space equals space fraction numerator 8 space straight x space 10 to the power of negative 3 end exponent over denominator open parentheses begin display style fraction numerator 1 plus space 2 space straight x space 10 space straight x 0.2 over denominator left parenthesis 0.4 right parenthesis squared end fraction end style close parentheses to the power of 1 divided by 4 end exponent end fraction
space equals space 3.6 space straight x space 10 to the power of negative 3 end exponent space straight m