Question 1

Which of the following best describes the difference between heat and work in terms of energy transfer?

Accepted Answer

Heat is energy transferred by random motion of particles, while work is energy transferred by ordered motion.

Question 2

A 70-kg man of height 1.55 m has a surface area estimated by $$Area = 0.202 	imes M$$^{0.425}$$ 	imes H$$^{0.725}$$. What is his approximate surface area?

Accepted Answer

$$1.7\ m^2$

Question 3

Which process is primarily responsible for the transfer of oxygen from the tear fluid to the cornea in the human eye?

Accepted Answer

Diffusion

Question 4

The first law of thermodynamics states that:

Accepted Answer

Energy, including heat, is conserved; it can be converted into another form, but the total amount remains constant.

Question 5

A drop of colored solution is introduced into a still liquid. Over time, the color spreads throughout the liquid. This process is called:

Accepted Answer

Diffusion

Question 6

The average kinetic energy of a molecule in an ideal gas is given by:

Accepted Answer

$$\frac{1}{2}mv^2$ = \frac{3}{2}kT$$

Question 7

Which of the following is the correct formula for the amount of heat conducted per second through a block of material?

Accepted Answer

$$H_c = \frac{K_cA}{L}(T_1$ - T_2$)$$

Question 8

During moderate physical activity, a 70-kg man consumes 260 Cal/hr. If 20% of this energy is used for external work, how much is converted to heat inside the body?

Accepted Answer

208 Cal/hr

Question 9

Which of the following statements about the second law of thermodynamics is correct?

Accepted Answer

Spontaneous changes in a system move from lesser to greater probability.

Question 10

The maximum ratio of work to heat input when heat flows from a region of higher temperature $$T_1 to $$lower temperature $$T_2 is $$given by:

Accepted Answer

$$\frac{Work}{Heat_{input}} = 1 - \frac{T_2$}{T_1$}$$

Question 11

Which of the following mechanisms is the primary way the human body cools itself during moderate physical activity in a warm climate?

Accepted Answer

Evaporation of sweat

Question 12

If the mean free path of a molecule in water is $$L = 10$$^{-8}$$ cm and its thermal velocity is v$$ = $$10^4 cm/s$$, what is the time required to diffuse a distance of 1 cm?

Accepted Answer

$$2.8\ h$$

Question 13

Which of the following factors does NOT affect the rate of heat outflow from the skin in cold conditions?

Accepted Answer

Skin color

Question 14

The rate of heat transfer by convection from the skin to the air is given by:

Accepted Answer

$$H_c' = K_c'A(T_s - T_a)$$

Question 15

Which of the following is true regarding the regulation of body temperature in humans?

Accepted Answer

Most heat is transferred from the inside of the body to the skin by blood in the circulatory system.

Question 16

Which of the following best explains why contact lenses should not be worn during sleep?

Accepted Answer

The cornea receives less oxygen by diffusion due to lack of blinking.

Question 17

The relationship between pressure $$P$$, volume $$V$$, and temperature $$T$$ for an ideal gas with $$N$$ molecules is:

Accepted Answer

$$PV = NkT$$

Question 18

If the skin is in contact with a good thermal conductor such as metal, which heat transfer mechanism is most significant?

Accepted Answer

Conduction

Question 19

Which of the following is the correct formula for the radiative energy exchange from the skin?

Accepted Answer

$$H_r = K_rA_r\epsilon(T_s - T_r)$$

Biophysics: Transformation of Energy and Thermodynamics in the Human Body

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