1. FORCES AND STRESSES

2. The Specification says you need to know:
Forces and stresses
Students should know and understand the impact of forces and stresses and the way in which materials can be reinforced and stiffened.
The forces and stresses are:
• Tension
• Compression
• Bending
• Torsion
• Shear
Materials can be enhanced to resist and work with forces and stresses to improve functionality
Students should know how materials can be reinforced, stiffened or made more flexible: eg
• Lamination
• Folding
• Webbing
• Fabric interfacing

8. Title:Forces
Copy the table on to your sheet. Fill in the table, the first one has been done for you.
Force
Description
Arrow Diagram
Example
Tension
Tension is the pulling force.
The strings on a guitar are under tension.
Compression
Torsion
Bending
Shear

9. Forces on a Bag Where will you find forces on a bag?
Label the bag picture you have been given with the different forces.
One of them is REALLY tricky and you will have to use your imagination!

10. The strap is under tension
When the clasp opens it shears
Objects in the bottom of the bag are compressing on the base.
The weight of the objects in the bag makes the bottom of it bend
And torsion?

11. Torsion? The bag strap getting twisted?
Removing the lid from make-up in the bag?
What did you come up with?

12. What can we do to counteract forces?
Lamination is layering materials
Bending is forming a flat material in to an angle
Folding is forming a flat material back on itself
Webbing is a very strong form of narrow fabric
Fabric interfacing is a way of adding thickness to a thin fabric
Copy the title and words in bold on to the reverse of your forces sheet.
You only need to copy the whole sentence if you need it to help you remember what the word means.

13. And we have learnt this all because...
When designing your bag you need to consider what forces will be applied to it.
And then consider what you can do to the materials you want to use to counteract the forces.
If you don’t think about forces when designing and making your bag, it may not be successful!
And of course forces need to be considered when designing and making any product, not just our bags!