How many food calories can a human burn up in an hour by exercising at this rate? (remember that only 20.0 % of the food energy used goes into mechanical

Human can produce a maximum mechanical power of 1/3 hp (horse-power).

Horse power is a unit of power, it equals 746 watt (watt is also a power unit, known to be equal to a joule per second)

So:

1 ph = 746 watt = 746 J/s

1/3 ph = 248.6 J/s

we're looking for the calories, so

1 joule = 0.239006 calories

So human produce a maximum mechanical power of:

248.6 J/s = 82.88 calories per second.

We're looking for the number of calories consumed in three hours, so:

82.88 cal/s = 82.88 cal/s * 3600 s * 3 = 895200 calories = 895.2 kilocalories (food calories).

The number of food calories is 895.2 food calories

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.

answer;

c. a tree whose roots are surrounded by wet sand.

explanation;

water stress is an important factor limiting the growth and productivity of forests.water stress is the most often cited cause of poor survival and growth of woody landscape plants.

-insufficient soil moisture is the most common form of water stress, but excess moisture that leads to poor soil aeration (hypoxia) can also result in reduced plant vitality. a tree whose roots are surrounded by wet sand would be least likely to experience water stress.