wiki Word:  Contact forces                                                                    

Definition: Contact forces are those types of forces which result when   the two interacting objects are perceived to be physically contacting each other. Examples of contact forces include frictional forces, tensional forces, normal forces, air resistance forces, and applied forces. Those forces and a few others are talked about in the table below:                                                  

In case you're wondering, the chain pictured below is an example of a tensional force.

This is because the chain is being held upwards from the top and at the same time, the marble is pulling down, thus creating tension.

 

 

 The picture with the parachute is an example of air resistance.

This is because as gravity pulls the parachute down, air resistance is forcing it up. 

 

 

The image with the water and the different balls in it shows buoyency.

Buoyency is a contact force which mostly depends on the mass and density of the object in the water.

If the object is more dense than the water, it sinks (like the golfball).

If the object is less dense (like the ping pong ball), then it stays above the surface.

If it has the same density as the water (like the other two balls), then it will stay halfway above, halfway below the water.

SO WHAT?!?

This term describes the force that is applied when at least two objects come in contact. It is the force that propells the objects away from eachother or holds them together. It also describes how different forces affect different objects. This term applies to everyday life because everytime two, three, four, or even more objects touch, they are representing contact forces. For example, when someone's fingers touch the buttons on a keyboard, they are demonstrating a contact force. There are many times in everyday life that you are around some sort of contact forces and some people don't even know that contact forces exist!!! We need to know about contact forces because without knowing what they are, we are unsure about their result. Without that, we wouldn't have parachutes and bowling lanes. We also wouldn't have been able to do alot of things because we wuld be so unsure of their result. With just knowing the definition to this simple word, we are able to uncover the mysteries many people used to ponder.

http://www.glenbrook.k12.il.us/gbssci/phys/Class/newtlaws/u2l2a.html , http://6turquoise.blogspot.com/