-         designers must understand the strengths and weaknesses of structural shapes, as well as the physical strengths and limits of the materials.

A.   Elastic Force

-        the force in deformed (stretched) matter that allows it to return to its original shape

B.    Flexibility

-        the materials ability to bend and move without distortion or damage

C.    Strength

- measure of how much load a structure can sustain.  This is measured by the amount of force a structure can withstand before failure occurs.

-         when one object rubs against another

-         it’s the force that resists the motion

A.    an example: driving a car there is friction between the tires and the concrete.  This keeps you on the road.

-         causes heat

B.                There are 2 ways to reduce friction.

1.                  keep parts well oiled or lubricated.

2.                Use ball bearings which allow the machine parts to move more freely

Newton’s laws of motion

1.                  Every object in motion will remain in motion unless an external force is applied to it.

2.                The relationship between an object’s mass, its acceleration, and force is F=ma

3.                For every action there is an equal and opposite reaction.

-the ability of a structure to withstand external forces is affected by its structural strength.

- Energy of motion- Energy that is transferred from a moving object to a stationary one.

A. Newton’s 1^st law of motion- an object moving at a constant speed will continue at that speed unless it is acted on by some other force.

B. 2^nd law of motion- acceleration of an object increases as the amount of the force applied on the object increases.

C. 3^rd law of motion- for every action there is an equal and opposite reaction.

This Blog is due April 30,2007.

As always, please proofread you essays before you post.

Due April 27, 2007

Please write a complete paragraph and double check your work for errors.  Remember to follow the checklist to make your writing interesting.

Use p 277 & 278 to guide their work.  They may use whatever materials they wish (cardboard, wood etc)

They must have a curtain that actually works (it may open vertically or horizontally)

This project is due on June 1, 2007

Force is the push or pull on an object. This is caused by object interacting with another object. When the interaction is finished the two objects no longer experience force.

Compression – forces squeezing together

Tension – pulling apart of a structure

Shear- Result of forces acting in opposite directions

Torsion- Twisting force

Vectors- arrows used to represent the direction and magnitude of a force.

- 2 parts:

i. tip

ii. tail

The tip points in the direction of the force.

The tail’s length indicates the strength of the force.

Gravity is the force that pulls you or an object toward the Earth.  This is responsible for the weight of bodies on Earth.

Gravitational force acts between objects, depending not only on the mass of each object but the distance between the objects.

Gravity is not a constant value across the universe.  The gravitational pull on the moon is only 1/6 of that on Earth.

Gravity actually pulls on the particles that make up the object.  The net force of the gravity on each particle is called the force of gravity. 

The point where the force of gravity acts is called the centre of gravity.

The position of the centre of gravity will affect the structure’s stability.

Stability- ability to stay standing and undamaged when acted upon by forces.

Some of the most complex structures are naturally occurring and can be found all around us.

                Examples:

                        Bird’s nest- frame               Mountain- Solid

                        Beaver Dam- frame               Caves- Shell

                        Ant Hill- Shell                 

                        Egg- Shell

                        Turtle Shell- Shell

                        Trees- Solid