Today you're going to do one of Mr. Tolboom's favorite physics problems of all time. If you don't like it, it obviously means you don't like Mr. Tolboom. That's cool, I guess. I mean, we don't have to be friends. I'll just go over here and cry now. No really don't worry about be, I know you hate me.

Anyway, first lets make sure you can use the circular motion equations. Solve this problem:

1. Mary is spinning a rock on a string. The rock has a mass of 5kg and the tension in the string is 36N. The string has a length of 0.5m.

     a. What is the centripetal acceleration of the rock? (7.2 m/s^2)

     b. What is the tangential velocity of the rock? (1.9 m/s)

     c. What is the period of the rock? (1.7 s)

OK, assuming you can do that, let's make sure you can still use Newton's Law of Universal Gravitation. Solve this problem:

2. The moon has a mass of 7.35e22 kg, the earth has a mass of 5.97e24 kg, and the distance from the earth to the moon is 3.84e8 m. Calculate the force due to gravity between the earth and the moon. (1.98e20 N)

Alright, now let's put it all together. The force due to gravity between the earth and the moon is the centripetal force that keeps the moon from flying off at a tangent. You know have everything you need to answer this question:

3. What is the orbital period of the moon? Don't forget units!