Let his weight be mg.
For a falling body in a fluid.
W - V - U = ma. Where W = Weight = 800N. m = mass V = Viscous Force = Air Resistance. U = upthrust = Negligible for air. a = acceleration g = acceleration due to gravity. Note also at terminal velocity a = zero.
W - V - 0 = m(0) 800 - V = 0 800 = V.
Therefore the viscous force which is equivalent to air resistance is also 800N. Cheers.
We call "terminal velocity" the constant speed of a falling body when it is no longer accelerating.
We know that if a body is not accelerating, then the net force on it is zero.
From the question, we know that the downward force of gravity on the skydiver is 800 N.
If the 800 N downward plus the air resistance upward add up to zero, then the air resistance upward must also be 800 N.
At terminal velocity, a skydiver weighing 800 N experiences an equal upward air resistance of 800 N. This balance of forces results in no net acceleration, allowing the skydiver to fall at a constant speed. Thus, the air resistance at terminal velocity is also 800 N.
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