# How long is the flea in the air for?

by quicknote
Tags: flea
 P: 33 I'm having problems with this question. I know it should be simple, but I can't seem to get the right answer. In this problem, you will use kinematic equations applied to a flea in free fall. Take the magnitude of free-fall acceleration to be g = 9.80 m/s^2. If a flea can jump straight up to a height of 0.550 m, what is its initial speed v_0 as it leaves the ground? My answer was 3.28 m/s, which is correct. How long is the flea in the air? I don't know which equations to use. to reach it's max height, I used: t=d/v and got 0.168s to reach the ground, I used: y1 = -0.5gt^2 and got 0.335s so the total time I calculate was 0.503s Can somebody help me? Thanks
HW Helper
P: 2,538
 Quote by quicknote If a flea can jump straight up to a height of 0.550 m, what is its initial speed v_0 as it leaves the ground? My answer was 3.28 m/s, which is correct. How long is the flea in the air? I don't know which equations to use. to reach it's max height, I used: t=d/v and got 0.168s to reach the ground, I used: y1 = -0.5gt^2 and got 0.335s so the total time I calculate was 0.503s Can somebody help me?
$d=r \times t$ only works for things that are moving at a constant speed.
For example, you could try using
$$0=v_0t-\frac{1}{2}gt^2$$
for the entire jump.

P.S. Do you think it's odd that the flea took longer to fall than to rise?