Question

For its size, the common flea is one of the most accomplished jumpers in the animal world. A 2.1 mm-long, 0.46 mg critter can reach a height of 17 cm in a single leap.

A) Neglecting air drag, what is the takeoff speed of such a flea?

I don't understand how I can find the velocity without being given the elapsed time, and I'd appreciate any help. Thank you.

Answer 1

Well, you will have to assume that the flea goes straight up.
The easy way to do it is to say the kinetic energy at takeoff equals the potential energy at the top when the speed is zero.
(1/2) m v^2 = m g h
or
v^2 = 2 g h
here g = 9.8 m/s^2
h = .17 meters