SMMART SCIENCE: Ringling Brothers and Barnum and Bailey Circus Globe of Steel

In the new "Dragons" Ringling Brothers and Barnum and Bailey Circus, eight members of the Torres Family taunt death as they speed their motorcycles around and around in the Globe of Steel.  "Once locked inside a 16-foot steel globe, all together they will orbit at an unprecedented 65 miles per hour within inches of each other. "

This is INSANE!  If you have ever seen this exhibition, it's a heart stopper.  I catch myself holding my breath as they whiz around and around each other.  It seems almost fake, like there is no way they can attempt this feat and not run into each other...yet, each real person goes into the Globe, rocks his bike in ready stance and zooms up into the controlled chaos!  Amazing!  Really, one of the most talented groups that Barnum and Bailey Circus showcases.

 The riders zoom on their bikes upside down in the globe and don't fall downward into each other.  How do their wheels stay on the steel, no matter what direction they proceed?  Even upside down?  This is a display of daring centrifugal force.

www.sciencenetlinks.com  explains that "Centrifugal force is a fictitious force associated with a rotating system, such as a merry-go-round on a playground. When the system stops rotating, the force seems to disappear. Another way to understand this force is to consider Isaac Newton’s First Law, “that an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by another force.” When you are pressed against a car door as the car goes around a curve, you may feel pushed outward, much as you would on a merry-go-round. Really, there is no force pushing you outward. Your body wants to go in a straight line, but the car holds you in, acting as the other force to make you go in a curved line. On the merry-go-round, you are holding yourself onto the ride, exerting a force that keeps you from flying off to travel in a straight line."  (http://sciencenetlinks.com/afterschool-resources/fun-forces/)

It goes on further to share the experience of riding in a car that is going fast.  Your body wants to continue in the straight line forward.  When the car turns around a corner, your wanting-to-go-straight-body presses against the side of the car.  The car is pulling you with it in the direction it is going, even though your body wants to go straight.  So there is this "fictitious force".

Now for the fun hands on activity to demonstrate that speed is necessary to keep people sitting in a roller coaster, and the Torres family motorcycle wheels on the steel.

Tie a piece of twine to the handle of a small bucket or sand pail.  Place a ball or penny into the bucket and have your child spin the bucket in a circle so the bucket goes upside down.  If your child spins quickly enough, the ball and penny will stay on the bottom of the bucket.  Ask your child if the penny will stay in the bucket if you swing more slowly? Have your child swing the bucket slowly.  What happens?  In order to swing the bucket in a circle at all, you will have enough speed that the penny stays in the bucket.  Ask your child what would happen if you turned the cup upside down? (The penny falls out.)

Let your child try swinging around some other objects.

Lets get daring.  Fill the bucket with a bit of water and ask your child if he thinks that the water would stay at the bottom of the bucket when he swings it over his head in a circle. (It doesn't matter if it's liquid, it will still experience centrifugal force.)