Planet with an 8.5 hour year!

Check out this exo planet (meaning planet outside of our solar system):
http://www.theregister.co.uk/2013/08/19/kepler_78b_fast_orbit/

What information would we have to have in order to tell how fast the planet is moving?
What info would we need to know what the magnitude of the force of gravity acting on the planet from the nearest star?
What would we need to know to figure the acceleration due to gravity on the planet itself?

Carousel at 6 flags

I went to six flags a couple of days ago and was trying to get my daughters to make an informed decision about which horse to choose.

The kid running the machine says, "the horses go 3 miles per hour" and I thought -- it's impossible that they all go the same speed. So, I decided to take a few measurements. This is what I got:
time for 1 revolution: 28.5 seconds.
outermost radius: approximately 33 ft
innermost radius: approximately 20 ft

So, was he right? Also, which horse is the better one to choose? Why?

Atwood machine -- plane vs blue whale cable strength

This is a cool problem to consider:
If you wanted to anchor an airplane into the ground so it wouldn't be able to take off, what would the rope have to be made out of?

Here is an answer for you. what-if.xkcd.com/56/

What's interesting is that they did not talk about how they came up with the blue whale weight. That would be a pretty easy force diagram to draw. Wanna try it?

Cool projectile motion photo

Just found this cool projectile motion photo in a Red Bull photo contest. Snowboarding never looked so educational!