Velocity

 

Once a Frisbee is thrown, it is given a velocity vector.  A vector has both a magnitude and a direction.  The velocity vector in the picture is denoted by a "U" with a bar over the top.

Now a vector is made up of components.  For this explanation we are going to look at the system with an upper and lower component. 

In the picture the disc is traveling from left to right, with an angular velocity component that is in a clock-wise rotation. (This can be thought of as a throw from a right-handed person using a standard backhand throw.) 

Now at the Frisbee rotates, the upper portion of the disc rotates with a velocity component pointing in the same direction as the overall velocity direction.  The lower portion rotates with a velocity pointing away from the overall velocity direction. 

So it can be thought of that the top potion has a higher velocity (because it is pointing in the same direction as the overall velocity) than the lower portion. (5)

 

Recalling what we learned about the Bernoulli Effect, we can say that the upper portion of the disc in the picture will experience a low region of pressure.  This would cause this side of the disc to rise, thus causing the disk to bank towards the opposite side.

 

While we are one the subject of velocity, we can figure out how to obtain a level flight.

 

For a level flight to occur, the lift force would need to be equal to the force "pulling" the disc to earth.  This force is the mass (m) of the Frisbee along with the acceleration of gravity (g).  We can make an equation for this force and set it equal to our lift force which we have already solved for:

 

Now using some simple algebra we can solve for our velocity (5).  

 

One last aspect about velocity.  Whenever an object travels through a fluid (in this case air) it experiences drag.  Drag is also a force, which has both a magnitude and a direction.  Drag acts parallel to and in the opposite direction of velocity.  It also opposes the lift force. 

 

 

 

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