A 30-N stone is dropped from a height of 10 m and strikes the ground with a speed of 13 m/s.
What average force of air friction acted on the stone as it fell?

4.1 N

Step-by-step explanation:

We can solve this problem by using considerations about energy.

At the moment the stone is dropped, it has only gravitational potential energy:

where

is the weight of the stone

h = 10 m is the initial height of the stone

As the stone falls, part of this energy is converted into kinetic energy, while part into thermal energy due to the presence of the air friction, acting opposite to the motion of the stone:

where:

is the mass

v = 13 m/s is the final speed of the stone

is the thermal energy

The thermal energy is actually equal to the work done by the air friction on the stone:

where

F is the average force of friction

h = 10 m

Since the total energy must be conserved, we can combine the three equations, so we find:

And solving for F, we find the average force of air friction:

"it's not the heat, it's the humidity".   that's a partly valid phrase you may have heard in the summer, but it's actually both.   the heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature.   this has important considerations for the human body's comfort.   when the body gets too hot, it begins to perspire or sweat to cool itself off.   if the perspiration is not able to evaporate, the body cannot regulate its temperature.   evaporation is a cooling process.   when perspiration is evaporated off the body, it effectively reduces the body's temperature.   when the atmospheric moisture content (i.e. relative humidity) is high, the rate of perspiration from the body decreases.   in other words, the human body feels warmer in humid conditions.   the opposite is true when the relative humidity decreases because the rate of perspiration increases.   the body actually feels cooler in arid conditions.   there is direct relationship between the air temperature and relative humidity and the heat index, meaning as the air temperature and relative humidity increase (decrease), the heat index increases (decreases).

step-by-step explanation:

1 number

if we use a graphing calculator, there is only one such number that satisfies the conclusion of the mean value theorem, that is, a number such that

where the right-hand side is the average rate of change of f on the interval [0.5,0.75], which is the slope of the secant line.

in the attached graph, the black line is the secant line which has its slope as the average rate of change of f on [0.5,0.75], while the orange line is the only tangent line to the graph of f in the interval that satisfies the mvt conclusion.