Most of the resistance of the human body comes from the skin, as the interior of the body contains aqueous solutions that are good electrical conductors. For dry skin, the resistance between a person's hands is measured at typically 500 kΩ. The skin varies in thickness, but on the average it is about 2.0 mm thick. We can model the body between the hands as a cylinder 1.6 m long and 14 cmin diameter with the skin wrapped around it.

(a) What is the resistivity of the skin?
Ω · m

(b) Compare your answer with the internal resistivity of the body, approximately

4.8 Ω · m.

rhoskin
rhointerior
=

How do you explain the fact that the resistance of the skin is about 1000 times greater than the internal resistance of the body, even though the resistivity of the skin is only about 60 times that of the interior of the body?

A )The skin has a smaller cross sectional area.

B )The resistance of an object scales exponentially with respect to the resistivity of the material out of which it is made.

C ) The skin is constantly moistened by biological processes.

D ) Charges can only exist on the surface of conductors.

Part f - example: finding two forces (part i) two dimensional dynamics often involves solving for two unknown quantities in two separate equations describing the total force. the block in (figure 1) has a mass m=10kg and is being pulled by a force f on a table with coefficient of static friction îľs=0.3. four forces act on it: the applied force f (directed î¸=30â above the horizontal). the force of gravity fg=mg (directly down, where g=9.8m/s2). the normal force n (directly up). the force of static friction fs (directly left, opposing any potential motion). if we want to find the size of the force necessary to just barely overcome static friction (in which case fs=îľsn), we use the condition that the sum of the forces in both directions must be 0. using some basic trigonometry, we can write this condition out for the forces in both the horizontal and vertical directions, respectively, as: fcosî¸â’îľsn=0 fsinî¸+nâ’mg=0 in order to find the magnitude of force f, we have to solve a system of two equations with both f and the normal force n unknown. use the methods we have learned to find an expression for f in terms of m, g, î¸, and îľs (no n).

Engineers find a new metal that is stronger than steel but much lighter. this material is also significantly cheaper than what is currently used for most aircraft, available in large quantities, and easy to manufacture. the engineers are excited because this new material will lower the costs of buying and operating airplanes for companies. what is probably the best step for the engineers to make next?

Place me with this question is my last question