Centripetal Force

Something I've always been interested in when it comes to robotics is centripetal force. To put it simply, centripetal force occurs whenever you have a mass rotating around another mass.  The first mass will seem to have a strong force pulling it away from the mass it's orbiting. That force is centripetal force. Here are some examples of centripetal force used with the NXT (the following projects were used without permission from the owners. I figured they would be ok with me using their awesome creations as examples, and if they are not, I hope they will notify me so I can remove them immediately. Thank you.):

PSYCLONE: THE RIDE
By NXTManiac

PSYCLONE: THE RIDE

This project is one of my favorite examples of centripetal force. Basically what happens is when the ride starts spinning, the chairs are pulled outward by the centripetal force. You may be wondering where the two masses are here. After all, doesn't the definition of centripetal force say that in order for the force to exist, we need two masses, one orbiting the other? Well in this case, there are a lot of individual masses going around a larger mass. Can you guess what those masses are? Well, the little masses are the chairs the minifigs are sitting on, and the large mass is the central tower. When the motor starts to spin, the centripetal force starts coming into play. The chairs seemingly want to get as far away from the central mass as possible, resulting in them actually moving higher into the air. This centripetal force is stronger than gravity. You know from past experience if you've ever been on a ride like this, that as the ride speeds up, the chairs move higher and higher. When it reaches it's highest speed, you have reached your highest point of the ground in your chair. Therefore we know that the amount of centripetal force in play is effected by the speed that the object is rotating.

The Enterprise

Now here's a question for you: What keeps the chairs rotating in a circle if they want to get as far away from the central object as possible? Well, in the Psyclone, it is the axles that connect the chairs to the center.  What happens if the centripetal force is stronger than the axles that are connecting the chairs to the center? The chair goes flying off. Although it may sound funny, it is actually very frustrating to the builder. I have had plenty of frustration in that area; when I was building "The Enterprise" I depended on the connections of 1x2 LEGO bricks to keep chairs from going flying. With it spinning at full power, it was quite a challenge. Many times I tried replacing the bricks hoping to find a stronger connection, but that only worked a few times.

Tower Crane

 

So now you might be wondering, what examples are there of centripetal force used in the NXT that doesn't have anything to do with amusement park rides? Well, there are plenty. They are just harder to find because they are less evident. Like the picture on the right of the Tower Crane by nxt2010nxt. When the motor turns the top structure, the load it is carrying will swing outward a little. Unlike PSYCLONE: THE RIDE and The Enterprise though, this creation doesn't rely on the centripetal force to make the project complete. However, it still would look unnatural if it didn't get pulled outward when the top turned.

Working Centrifuge

Another example of centripetal force is in a centrifuge. Snabeli in his project named "Working Centrifuge" build a very good example of a centrifuge with an NXT set. A centrifuge is a machine that rapidly spins objects around a central axis which creates high amount of centripetal force. In laboratories it spins test tubes and is it used to separate solids from liquids or separate out liquids of different densities.