Forces and Failures

There are four types of forces, and each type causes its own failure mode:
Tension-When a material is pulled from either end it will elongate,  and eventually  it will "snap," meaning the material breaks into two pieces.

Compression-When a material is pushed together from opposite sides  there are two possible outcomes. 1) The material can bend, or "buckle" under the force.
2) The material will shift, or "shear," where different parts move in different directions.

Torsion-Twisting the ends of a material in opposite directions will eventually cause  the material to shift passed itself,  meaning the failure method is similar to a compression  failure, in this case it is known as "twist."

Shear-Pushing different parts of material too far in  different directions results in a failure known as "shear."

Mass vs. Weight

Read through this note. 

Weight is the force exerted by a mass because of gravity, measured in Newtons.

Mass is the amount of matter in an object, measured in kilograms.

The mass of an object does not change with gravity, but the weight will.  

The moon has 1/6 the gravity of earth, meaning you would weigh 1/6 of  your earth weight while on the moon, however your mass is the same.

When you use a scale you are actually using weight to make it work.   However, the scale gives a reading of mass.  This works because the scales have been calibrated to convert the value of force exerted on it, into a reading of mass.

There are several different types of scales, but all work on similar principles A force is exerted on it, something movies, a reading is given.

Joints

Joining Technology

 A joint is any place on a structure where pieces are held  together. 

1.  Joints are important for many reasons:

 2. Allow the use of multiple materials

3. Allow a structure to have different components

o Without joints, a structure would have to be carved or mold   “Mobile Joints” are joints that allow movement.

-->Your shoulder is a ball and socket joint

• “Rigid Joints” prevent movement.

 -->A stool has a rigid joint between the seat and legs

•Your task for today is to read a section of text and  make a note with the title 

"Joining Methods"  

•In your note, you should cover the following topics,  including a brief explanation and example of each:

o Mobile vs Rigid Joints

o Fasteners

o Ties

o Adhesives

o Melting

o Interlocking Shapes 

•Joints are normally the weakest point  of  structure, therefore there is a  need for a variety of 

types of joints to suit a variety of different situations.

Forces Intro

Using word or a piece paper. Answer the following questions. You can use your textbook or research online.


1. What is a force?


2. What are some external forces that act on structures? Give some definitions and/or examples.


2. What are some internal forces that act on structures? Give some definitions and/or examples.