How do I find out the kinetic energy of a yoyo?

I'm so glad you asked that...

The kinetic energy of an object can be determined by multiplying the mass of the object (in kilograms) times the velocity its travelling (in meters/sec) times its velocity again and then dividing the whole number by 2. This gives the value of energy in units of joules, the metric unit of energy.
However, since the yoyo is spinning, you also need to take into account its rotational kinetic energy. This is determined by multiplying the mass of the object times its radius (in meters) times the rotational velocity (revolutions per second) times the rotational velocity again and dividing the result by two.
Once you have both these values, you add them together to get the total kinetic energy.

Now I hope you took notes - quiz on Monday!

http://www.cosi.org/resources/askCosi/encyclopedia.asp?qid=10&hotWord=energy

Thanks Tex! But can we do the quiz on tues...I may need more time for this one!

Samantha:
If you look at this a little differnt you can get your answer.
First assume no friction.
Now you know that the yoyo has dropped, by the force of gravity, the lenght of the string.
At the end of the string the rotational energy should equal the energy the yoyo would have had if it free fell that distance.

Now for my quiz:

I won't figure the energy for you because:
A. I'm too lazy
B. I can't remember how.
C. All of the above.

Regards Mike b. (AKA Byter)

LOL thanks Byter!