Question

If a flea can jump straight up to a height of 21.1 cm , what is its initial speed as it leaves the ground, neglecting air resistance?

Answer 1

The flea jumps at high velocity, reaches zero velocity at the maximum height 21.1 cm before starting to fall. Solve for initial velocity given final velocity is zero.
since time is not given, use the equation:
v^2 = u^2 + 2as
convert gravity or displacement to have same units. 9.8 m/s = 980 cm/s
0 = u^2 + 2(-980)(21.1)
41356 = u^2
sqrt(41356) = u
203.4 cm/s = u

Answer 2

Answer:

Initial speed, u = 2.03 m/s

Explanation:

Flea jumps to a height of, h = 21.1 cm = 0.211 m

As it leaves the ground, its final speed, v = 0

Acceleration, a = -g

Let u is the initial speed of the flea. It can be calculated as :

$v^2-u^2=2as$

$-u^2=2\times (-9.8)\times 0.211$

u = 2.03 m/s

So, the initial speed of the flea as it leaves the ground is 2.03 m/s. Hence, this is the required solution.