How Do You Solve These Two Pressure Calculation Problems?

[Vingen]

I'm doing an online quiz for my course, however the system does not accept my answers for these 2 problems. Could you tell me how to solve them.

1. If a vacuum gauge connected to a chamber gives a reading of 41 kPa where the local atmospheric pressure is given as 1.01325 bar, what is the absolute pressure in the chamber? Give your answer in Pa and correct to 4 significant figures in scientific notation eg 4.535e4 uses four significant figures but 4.5350e4 uses five.

My answer was 1.423x10^5 Pa



2. If the fluids contained in a container are layered from the bottom to the top as shown.
http://www.picvalley.net/u/43/10566_493.JPG
What is the pressure at point 1 given fluid 1 has a density of 622kg/m3 and h1 is 210mm, fluid 2 has a density of 952 kg/m3 and h2 is 84mm and fluid 3 has a density of 13,637 kg/m3 and h3 is 60mm. Take g = 9.8m/s, Patm = 1.01325 bar and give your answer in kPa correct to 5 significant figures.

My answer here was 111.40732 kPa

 

[Nate810]

The answers to both questions are correct. If the system is not accepting your answers, it may be due to a formatting issue or a typo. Make sure you are using the correct units and that your answer is in the correct format. Additionally, double check that all of your numbers are correct and that you are not making any typos.

 

[ogb p]

To solve the first problem, we can use the formula P = P0 + ρgh, where P is the absolute pressure, P0 is the local atmospheric pressure, ρ is the density of the fluid, g is the acceleration due to gravity, and h is the height of the fluid column. In this case, P0 = 1.01325 bar, ρ = 0 (since it is a vacuum), g = 9.8m/s^2, and h = 0. Therefore, the absolute pressure in the chamber is P = 1.01325 bar = 1.423x10^5 Pa.

For the second problem, we can use the same formula, but we need to take into account the different densities and heights of the fluids. We can start by calculating the pressure at point 3, using P3 = P0 + ρ3gh3 = 1.01325 bar + (13,637 kg/m^3)(9.8m/s^2)(0.06m) = 1.01325 bar + 8.0034e3 Pa = 1.0212534 bar. Then, we can use this pressure at point 3 to calculate the pressure at point 2, using P2 = P3 + ρ2gh2 = 1.0212534 bar + (952 kg/m^3)(9.8m/s^2)(0.084m) = 1.0212534 bar + 8.0024e3 Pa = 1.0292558 bar. Finally, we can use this pressure at point 2 to calculate the pressure at point 1, using P1 = P2 + ρ1gh1 = 1.0292558 bar + (622 kg/m^3)(9.8m/s^2)(0.21m) = 1.0292558 bar + 1.287444 Pa = 1.030543244 bar. Converting this to kPa and rounding to 5 significant figures, we get 111.41 kPa.

It's important to double check your calculations and units to ensure you are using the correct values and conversions. Also, make sure to pay attention to significant figures when rounding your final answer.