WAEC Physics 2015 Objective — Question 4
Question 4 of 50 from the West African Examinations Council (WAEC) Physics 2015 Objective paper, with the correct answer and a full explanation.
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The barometric reading at a place is 73.5 cm Hg. Calculate the pressure at a point 30 m below the surface of water contained in a reservoir at the place. [g = 10 ms⁻², density of mercury 13.6×10⁴ kg m⁻³, density of water = 1.0×10³ kg m⁻³]
- A. 4.0×10⁵Nm⁻²Correct
- B. 3.0×10⁵Nm⁻²
- C. 2.0×10⁵Nm⁻²
- D. 1.0×10⁵Nm⁻²
Explanation
Converting the barometer reading to Pascals gives about 1.0×10⁵ N/m². Adding the pressure due to the 30 m water column (ρgh = 1000×10×30 = 3×10⁵ N/m²) gives a total pressure of about 4.0×10⁵ N/m².
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