Question:

Mercury is filled in a tube of radius 2cm2 \, \text{cm} up to a height of 30cm30 \, \text{cm}. The force exerted by mercury on the bottom of the tube is ___N.
(Given, atmospheric pressure = 105N/m210^5 \, \text{N/m}^2, density of mercury = 1.36×104kg/m31.36 \times 10^4 \, \text{kg/m}^3, g=10m/s2g = 10 \, \text{m/s}^2, π=227\pi = \frac{22}{7})

Updated On: Mar 22, 2025
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Correct Answer: 177

Solution and Explanation

The force exerted by mercury on the bottom of the tube can be calculated as:
F=P0A+ρmghA F = P_0A + \rho_m ghA  
where: 
- P0=105Nm2 P_0 = 10^5 \, \text{Nm}^{-2} (atmospheric pressure), 
- A=πr2=227×(2×102)2 A = \pi r^2 = \frac{22}{7} \times (2 \times 10^{-2})^2 (area of the base), 
- ρm=1.36×104kg m3 \rho_m = 1.36 \times 10^4 \, \text{kg m}^{-3} (density of mercury), 
- g=10ms2 g = 10 \, \text{ms}^{-2}
- h=30×102m h = 30 \times 10^{-2} \, \text{m} (height of mercury column). 
Calculating A A
A=227×(2×102)2 A = \frac{22}{7} \times (2 \times 10^{-2})^2  
Substitute into the force equation: 
F=105×227×(2×102)2+1.36×104×10×(30×102)×227×(2×102)2 F = 10^5 \times \frac{22}{7} \times (2 \times 10^{-2})^2 + 1.36 \times 10^4 \times 10 \times (30 \times 10^{-2}) \times \frac{22}{7} \times (2 \times 10^{-2})^2  
Solving this: 
F=51.29+125.71=177N. F = 51.29 + 125.71 = 177 \, \text{N}.

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