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QJEEM23Phc0aa: JEE Main 2023 Physics - Class 11 JEEM23Phc0aa Solution: Glycerin of density is flowing through the conical section of…

Glycerin of density 1.25×103 kg m−31.25 \times 10^{3} \mathrm{~kg} \mathrm{~m}^{-3} is flowing through the conical section of pipe The area of cross-section of the pipe at its ends are 10 cm210 \mathrm{~cm}^{2} and 5 cm25 \mathrm{~cm}^{2} and pressure drop across its length is 3 Nm−23 ~\mathrm{Nm}^{-2} . The rate of flow of glycerin through the pipe is x×10−5 m3 s−1x \times 10^{-5} \mathrm{~m}^{3} \mathrm{~s}^{-1} . The value of xx is ___________.

Step-by-Step Verified Solution

We can use the Bernoulli equation and continuity equation to solve this problem. The Bernoulli equation is given by:

P1+12ρv12=P2+12ρv22P_1 + \frac{1}{2} \rho v_1^2 = P_2 + \frac{1}{2} \rho v_2^2

The continuity equation is given by:

A1v1=A2v2A_1 v_1 = A_2 v_2

From the given data, we have:

P1−P2=3 Nm−2P_1 - P_2 = 3 \mathrm{~Nm}^{-2} A1=10 cm2=10×10−4 m2A_1 = 10 \mathrm{~cm}^2 = 10 \times 10^{-4} \mathrm{~m}^2 A2=5 cm2=5×10−4 m2A_2 = 5 \mathrm{~cm}^2 = 5 \times 10^{-4} \mathrm{~m}^2 ρ=1.25×103 kg m−3\rho = 1.25 \times 10^3 \mathrm{~kg} \mathrm{~m}^{-3}

Rearrange the continuity equation to solve for v2v_2 :

v2=A1A2v1=2v1v_2 = \frac{A_1}{A_2} v_1 = 2v_1

Substitute v2v_2 and rearrange the Bernoulli equation:

P1−P2=12ρ(v22−v12)P_1 - P_2 = \frac{1}{2} \rho (v_2^2 - v_1^2)

3=12×1.25×103(4v12−v12)3 = \frac{1}{2} \times 1.25 \times 10^3 (4v_1^2 - v_1^2)

Now, solve for v1v_1 :

3=12×1.25×103×3v123 = \frac{1}{2} \times 1.25 \times 10^3 \times 3v_1^2 v12=31.875×103v_1^2 = \frac{3}{1.875 \times 10^3}

v1=31.875×103v_1 = \sqrt{\frac{3}{1.875 \times 10^3}}

v1≈0.0400 m s−1v_1 \approx 0.0400 \mathrm{~m} \mathrm{~s}^{-1}

Now, calculate the rate of flow of glycerin through the pipe (volume flow rate) using v1v_1 and A1A_1 :

Q=A1v1Q = A_1 v_1

Q=10×10−4×0.0400Q = 10 \times 10^{-4} \times 0.0400

Q=4×10−5 m3 s−1Q = 4 \times 10^{-5} \mathrm{~m}^{3} \mathrm{~s}^{-1}

So, the rate of flow of glycerin through the pipe is 4×10−5 m3 s−14 \times 10^{-5} \mathrm{~m}^{3} \mathrm{~s}^{-1} , and the value of xx is 4.

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