What's the terminal velocity of an average sloth, anyways?
Science time!
Terminal velocity is equal to the square root of 2mg/AC, where m is the mass of the object, g is acceleration due to gravity, A is the projected area of the object, and C is the drag coefficient.
I'm going to use an average brown-throated three-toed sloth for this, as it is the most common.
Drag coefficient and projected area are very awkward numbers to estimate for the irregular shape of a sloth.
I will assume that the sloth curls up into a ball in terror for this example, so that I can use the coefficient for a sphere (~0.5).
To calculate projected area, I will use half body length as the radius of a sphere. The average sloth is 42 to 80 centimetres long, giving 21 to 40 centimetres as the radius. I'll use 30 here.
The projected area of a brown-throated sloth in the foetal position is 4*pi*r
2, where r is 0.3 metres, giving us 1.13 square metres.
The average sloth weighs 2.25 to 6.3 kilograms, so, again, I'll be using 3.5 for convenience's sake.
Putting all these numbers together gives us (2 * 3.5 * 9.81) / (1.13 * 0.5), and assuming I haven't made any terrible mistakes, the terminal velocity of the average sloth in the foetal position
is 121.5 ms-1. 11 ms
-1, because I forgot the square root. Which is roughly 40 kmph, or 25 mph.