Air drag and air-pressure on the inner surface of the the parachute: Upwards
Explanation:
If a sky-diver is in the final stages of his descend with open parachute such that the wind is calm and it does not blows him laterally.
In such a condition the air resistance in the form of drag and the pressure force due to the air captured in the parachute are acting in the upward direction which balance the force of gravity on the body. But this situation may occur momentarily and then again the diver must begin to slowly descend.
The relationship of the speed of sound, its frequency, and wavelength is the same as for all waves: vw = fλ, where vw is the speed of sound, f is its frequency, and λ is its wavelength.
