3.3 Terminal velocity: example

Course subject(s) 3. Drag force

EXAMPLE 3.3A: SPEED OF A FALLING HAILSTONE (ELEMENTARY)

Consider a hail stone falling at its terminal velocity. We consider a big one: its diameter is 5cm.
What is the terminal velocity of this hail stone?

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EXAMPLE 3.3B: PARACHUTIST AT TERMINAL VELOCITY (MEDIUM)

In this exercise, we will estimate the terminal velocity of a paratrooper coming down at their terminal velocity after jumping out of a plane.

We will estimate the mass of the paratrooper, including their parachute, as 100 kg. The parachute, when opened, will have a diameter of about 10 m.

Note that the air density is 1.2 kg/m3

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In the theory, you have seen the students and one of the teachers sky diving in a wind tunnel. Obviously, the upward wind is blowing past the sky divers at a high velocity, much higher than the relative velocity past a sky diver with a parachute.

In this exercise, you are challanged to estimate the velocity of the wind. The challange is that no additional information is provided: you need to model this your self and make estimates of the relevant parameters and quantities.

If you can do this, you really are well on your way to mastering Transport Phenomena! If not, don’t worry: this is an advanced exercise.