Sunday, July 20, 2014

Physics of Football. Aerodynamics. Instructions for a styrofoam glider.



Science Blog              from        scienceofeverydaylife.discoveryeducation.com (author?)

Introduction
After finishing the turkey for Thanksgiving dinner, I was able to partake in another Thanksgiving Day tradition:     watching football.   I played football through my high school years, and I coached high school football during my teaching career . I absolutely love the game! 

When coming up with ideas for this blog, there is no more obvious place for me to look for physics to appear than on a football field.   Gravity ,   mass,   weight, and   motion all play a vital role in the game. There are 300-pound linemen tackling 180-pound running backs, kicking, running, punting and throwing. All of these actions are carefully orchestrated within the laws of physics.

As a kid, one of the first things I was taught about football was how to throw it.   Placing your fingers on the ball, the proper release, and the proper angle to release the ball at:    all of this leads to being able to throw a perfect spiral.   Why a spiral?   Why not throw the ball end-over-end?   The obvious answer is because it is easier to catch that way,  but is there another reason?

The Principles
There are a few concepts we need to address in order to answer this question.
  • Forces
  • Newton 's Laws of Motion
  • Friction (Aerodynamics)
The Science
What is a force?
Simplified, a force is a push or a pull on an object.     In order for an object to move      (or stop moving),   a force  must  first  be  applied  (see  Newton 's Law's below).    Objects  do not move (or stop moving) just because a force is applied to them, either.
Forces can be added and subtracted.    If two forces are working in the same direction, they are added together.   An example of this occurs during a car accident when a car rear-ends another.       The force of the car from behind is added to the force of the car that gets hit.   

If two forces are working in  opposite directions  of each other,   they are subtracted.    An example of this occurs when you sit in a chair.   Gravity is pulling you downward, and the chair is pushing you upward.  These forces are equal   (they cancel each other out),   so there is no motion. 

When throwing a football, the quarterback certainly must apply a force to the football  in order to get it to his receiver, but are there any other forces at work on the football? The  answer   is   yes     the   two   biggest   forces   being   gravity   and   wind   resistance     (a frictional force often called drag). 

Gravity causes the ball to fall towards the ground   (Add the forces), and wind resistance works in the opposite direction of the force that the quarterback applies to the ball (Subtract the forces).

What are Newton's Laws of Motion?
Sir Isaac Newton is credited with the development of three laws of motion that have governed classical mechanics . Newton's Laws of Motion are:
1.      An object at rest stays at rest and an object in motion stays in motion unless acted upon by an outside force.    (To read more about Newton's First Law of Motion, see this article.)
2.      Force is equal to an object's mass times its acceleration. (To read more about Newton's Second Law of Motion, see this article.)
3.      For every action, there is an equal and opposite reaction. (To read more about Newton's Third Law of Motion, see this article).

What role does friction play?
Friction is a force that opposes motion.    It occurs when two surfaces rub past each other.  Every surface has a different   coefficient of friction.   This  coefficient of friction essentially tells us how "rough" the surface is.    The greater the coefficient of friction,  the more "rough" the surface.    When an object moves  through the air,  we call the resulting frictional force   wind resistance, or drag.
Aerodynamics is the study of forces and the resulting motion of objects through the air. Essential aerodynamics looks at ways to reduce wind resistance.   To read more about aerodynamics, see this article.

Answer to the Question
Basically, the reason to throw a football in a spiral has to do with the most efficient way to move the football through the air.   The spiral helps to reduce the amount of surface area the ball is exposed to.   This lowers the effect of wind resistance on the ball, and it allows the ball to travel at a greater speed and a further distance.
____________________________________________

 STYROFOAM GLIDER
See how different structural changes influence the distance it travels.

Try This!
To investigate air resistance, aerodynamics and forces, try making a styrofoam glider.   Possible variables to study:
  • Effect of mass on distance
  • Effect of length of fuselage on distance
  • Effect of length of wing on distance
  • Effect of length of tail on distance
  • Effect of wing shape on distance
  • Effect of tail shape on distance
  • Effect of fuselage shape on distance
Materials:
  • Scissors
  • Styrofoam plate
  • Paper clips
Design:
1.      Using the scissors, cut a fuselage, wing and tail out of the plate.
2.      Take  the  fuselage  and,  using  the  tip  of  the  scissors, cut a hole in the middle  for wings.
3.      On the back end of the fuselage, clip out a small triangle  to insert the tail.
4.      Place a paper clip on the nose of the plane for support.

Thursday, July 10, 2014

GOOD NEWS, ESPECIALLY FOR PARENTS OF YOUNG KIDS



Dear Parent,

I believe that physics can be learned by children through games and sports.

Physically, we understand this, for example:


If we’re off balance, we instinctively put our arms out, and move our feet apart   (for a better center of gravity).


If we’ve hit something too hard, we want to remember to use less force the next time.


As we struggle to pedal a bike uphill (using a lot of energy), going downhill  we may need to use the brakes or we’ll go faster and faster (due to the way gravity works).


The above are just a few examples of how everything we do involves physics.

Basically, what I do is give a name to what our bodies already know.  
 Using language leads to deeper understanding.  
I also like to demonstrate the same principle in different ways (the more reinforcement, the better).


You can start by concentrating on just two things:


GRAVITY    and    ENERGY


Explain that gravity is something that is all around us, we cannot see it-- but we can feel what it does.  It pulls things down, it keeps things down.  So when I’m climbing uphill, it is harder work, because gravity is pulling me down when I am going up.    I have to use a lot of my energy.  But when I go downhill, it’s easier because now gravity helps me, and I can use less of my energy. 


These are some of the examples I’ve used:

            Sledding story (read it further on in this blog)

            Blowing bubbles  (energy to blow the bubbles, gravity to pull them down)

            Volleyball with a beachball or balloon (I call it Volleyballoon)

            Jumping   (jumping over a puddle; jump rope; doing the “Hokey Pokey”).   
            ---a lot of energy is used in moving your whole body when you jump  
            ---jumping up against the pull of gravity!


Slide in the playground---This could be a way for you to get started teaching science to your child.   
Remember:  More energy needed going up due to the pull of gravity.  
                   Less energy needed going down because the pull of gravity helps you.
                   (no work – let gravity do it for you).   I call this the “Whee !” factor.


Some children will quickly understand the idea of gravity;  some won’t right away.         At some point they will get it.  


Being aware of and understanding physics in daily activities will help physics to make sense when it is studied later. 

Try it!  You can do it.  Thanks!

Kathy

Monday, July 7, 2014

The Physics of Baseball: "You Can Observe A Lot By Watching..."


This is a lecture (runs about an hour and a half) that looks good.

                www.youtube.com/watch?v=jVXIX9jc3dw



The Science of Softball

I found this on the web.  Haven't had time to read and view all of it, but from what I see it looks very good.  It's a college student's assignment.

             www.slideshare.net/cahisch/the-science-of-softball-2531016