Change the chapter
Question
Pressure in the spinal fluid is measured as shown in Figure 11.46. If the pressure in the spinal fluid is 10.0 mm Hg: (a) What is the reading of the water manometer in cm water? (b) What is the reading if the person sits up, placing the top of the fluid 60 cm above the tap? The fluid density is 1.05 g/mL.
Question Image
<b>Figure 11.46</b> A water manometer used to measure pressure in the spinal fluid. The height of the fluid in the manometer is measured relative to the spinal column, and the manometer is open to the atmosphere. The measured pressure will be considerably greater if the person sits up.
Figure 11.46 A water manometer used to measure pressure in the spinal fluid. The height of the fluid in the manometer is measured relative to the spinal column, and the manometer is open to the atmosphere. The measured pressure will be considerably greater if the person sits up.
Question by OpenStax is licensed under CC BY 4.0.
  1. $13.6 \textrm{ cm H}_2\textrm{O}$
  2. $76.6 \textrm{ cm H}_2\textrm{O}$
Solution Video

OpenStax College Physics for AP® Courses Solution, Chapter 11, Problem 75 (Problems & Exercises) (1:53)

Sign up to view this solution video!

Rating

No votes have been submitted yet.

Quiz Mode

Why is this button here? Quiz Mode is a chance to try solving the problem first on your own before viewing the solution. One of the following will probably happen:

  1. You get the answer. Congratulations! It feels good! There might still be more to learn, and you might enjoy comparing your problem solving approach to the best practices demonstrated in the solution video.
  2. You don't get the answer. This is OK! In fact it's awesome, despite the difficult feelings you might have about it. When you don't get the answer, your mind is ready for learning. Think about how much you really want the solution! Your mind will gobble it up when it sees it. Attempting the problem is like trying to assemble the pieces of a puzzle. If you don't get the answer, the gaps in the puzzle are questions that are ready and searching to be filled. This is an active process, where your mind is turned on - learning will happen!
If you wish to show the answer immediately without having to click "Reveal Answer", you may . Quiz Mode is disabled by default, but you can check the Enable Quiz Mode checkbox when editing your profile to re-enable it any time you want. College Physics Answers cares a lot about academic integrity. Quiz Mode is encouragement to use the solutions in a way that is most beneficial for your learning.

Calculator Screenshots

OpenStax College Physics, Chapter 11, Problem 75 (PE) calculator screenshot 1
Video Transcript
This is College Physics Answers with Shaun Dychko. The pressure reading in the water manometer is going to be 10 millimeters of mercury converted into centimeters of water. So we have a conversion factor that's given to us in the textbook between millimeters of mercury and Pascals, and then again from Pascals to centimeters of water. So we have 133 Pascals for every one millimeter of mercury and then we multiply that by one centimeter of water for every 98.1 Pascals. We end up with 13.6 centimeters of water. Now if the person sits up then they will be adding an additional pressure due to the height of the column of spinal fluid. So we have to figure out what this term is and then add that to P naught which is this pressure when lying down. So this is P naught here. So rho g h, well, we need to change this density into kilograms per cubic meter. So we have 1.05 grams per milliliter and then we convert that into centimeters cubed, then turn that into meters cubed on the bottom by multiplying by 100 centimeters for every meter three times, and then we multiply by one kilogram for every 1000 grams. We're left with kilograms per cubic meter. Then multiply by g which is 9.81, then times the height in meters, so 60 centimeters times one meter for every 100 centimeters. Then we want to convert this into centimeters of water. So there's one centimeter of water for every 98.1 Pascals. This makes 63 centimeters of water. So we add that to 13.6 centimeters when lying down. This works out to 76.6 centimeters of water.