How Does Air Resistance Affect a Flea's Jump Height?

[Jaklynn429]

Homework Statement

Fleas have remarkable jumping ability. If a 0.50 mg flea jumps straight up, it will reach a height of 36 cm if there is no air resistance. In reality, air resistance limits the height to 18 cm.

Homework Equations

K=1/2 m*v^2

The Attempt at a Solution

I tried to use kinematics to get a delta T, and the program is still saying I am wrong! The final is tomorrow and this is a practice problem, can someone please explain how to do this! thanks!

 

[glueball8]

What is the problem?? Is it asking for how much energy is used up by air resistance?

 

[Jaklynn429]

I'm sorry! The problem wants to know:
a) what the flea's kinetic energy is as it leaves the ground?
b) at its highest point, what fraction is converted to potential energy?

 

[glueball8]

I'm assuming "a) what the flea's kinetic energy is as it leaves the ground?" is for
"Fleas have remarkable jumping ability. If a 0.50 mg flea jumps straight up, it will reach a height of 36 cm if there is no air resistance."

and "b) at its highest point, what fraction is converted to potential energy?" is for "In reality, air resistance limits the height to 18 cm."

For a) energy is conserved. soo we pick the lowest point that has a gratational potential of zero. so we can use this

$$\frac{1}{2}mv^2=mgh$$

 

[Jaklynn429]

Here is my problem though...the statement doesn't separate those two things. The problem reads exactly this: "Fleas have remarkable jumping ability. If a 0.50 mg flea jumps straight up, it will each a height of 36 cm if there is no air resistance. In reality, air resistance limits the height to 18 cm."
a) what is the flea's kinetic energy as it leaves the ground?

That's my issue, I don't know whether to use the 36 or the 18.

 

[LowlyPion]

Here is my problem though...the statement doesn't separate those two things. The problem reads exactly this: "Fleas have remarkable jumping ability. If a 0.50 mg flea jumps straight up, it will each a height of 36 cm if there is no air resistance. In reality, air resistance limits the height to 18 cm."
a) what is the flea's kinetic energy as it leaves the ground?

That's my issue, I don't know whether to use the 36 or the 18.

You use 36. That's what the problem is telling you when it says if ...

 

[glueball8]

Is there even a part b)? it would be pointless if you use point 36 for part b) because it would be 100%, of course.