How much time is it in the air?

a) If a flea can jump straight up to a height of 0.520 m, what is its initial speed as it leaves the ground?
b) For how much time is it in the air?

1 Answer
Harish Chandra Rajpoot
Jul 4, 2018

3.194\ m/s & 0.6512 \ s

Explanation:

If u is the initial upward speed of flea to reach a maximum vertical height h=0.52\ m against the gravity where its velocity becomes zero i.e. v=0

Now, from third equation of motion

v^2=u^2+2as

For motion against gravity

v^2=u^2-2gh

0^2=u^2-2(9.81)(0.52)

u=\sqrt{2\cdot 9.81\cdot 0.52}

=3.194\ m/s

The taken t by flea to reach to maximum height where final velocity v=0, is given from first equation of motion

v=u+a t

For motion against gravity

v=u-g t

0=3.194-9.81t

t=0.3256\ s

hence, total time when flea remains in the air

=2\times 0.3256

=0.6512\ s

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