Change the chapter
A walrus transfers energy by conduction through its blubber at the rate of 150 W when immersed in $-1.00 ^\circ\textrm{C}$ water. The walrus’s internal core temperature is $37.0^\circ\textrm{C}$, and it has a surface area of $2.00 \textrm{ m}^2$. What is the average thickness of its blubber, which has the conductivity of fatty tissues without blood?
Question Image
Walrus on ice. (credit: Captain Budd Christman, NOAA Corps)
Walrus on ice. (credit: Captain Budd Christman, NOAA Corps)
Question by OpenStax is licensed under CC BY 4.0.

$10 \textrm{ cm}$

Solution Video

OpenStax College Physics for AP® Courses Solution, Chapter 14, Problem 37 (Problems & Exercises) (2:23)

Sign up to view this solution video!


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 14, Problem 37 (PE) calculator screenshot 1
Video Transcript
This is College Physics Answers with Shaun Dychko. We have a walrus with an internal temperature which we call T2 since this is where the thermal energy is coming from and it's going towards this other body which is T1, namely the sea water, which is at negative 1 degree Celsius and T2 the internal body temperature is that of a mammal which is 37 degree Celsius and there is this insulating layer of blubber and we have to figure out what the thickness is in this question. Now we're told that the rate of heat transfer is a 150 watts and so that's Q over t in this rate of heat transfer due to conduction formula and the total area of the walrus is 2 square meters and the thermal conductivity of this material is that of fatty tissue without too much blood vessels and I think that is the wording that it said. Yeah fatty tissue without blood. Okay. So we have to solve this for d and we multiply both sides by d and divide both sides by this fraction Q over t and so we are gonna think of Q over t as a single thing that we're dividing by so on this side we multiply by d and we divide by Q over t and then Q over t cancels here and the d cancels over here. If this looks a bit strange, you might prefer instead of dividing by Q over t I often like to multiply by its reciprocal so we can multiply by the reciprocal of t over Q and now clearly the Q's and t's cancel. So, d is thermal conductivity times the area multiplied by the difference in temperatures divided by the rate of heat transfer. So that’s 0.2 Joules per second per meter per Celsius degree thermal conductivity for fat multiplied by the area 2 square meters surface area of the walrus multiplied by the difference in temperature which is 37 degree Celsius minus negative 1 degree Celsius and keeping in mind that that makes a plus, minus and a minus, divide by 150 Watts and that gives 10 centimeters must be the thickness of the fatty tissue insulating the walrus.