EXERCISES:

Page 92, exercises 1-2

1.Copy and complete the following table:

Type of structures	Examples
Mass	Walls, dams, etc.
Frame structures	Building
Truss Structures	Electricity pylons
Suspended stuctures	Bridges, marquees, etc.

 
2.Have you seen a structure that uses cables? Write down the names of ones that you can remember or the ones that you can see.


Electricity pylons

Page 93, exercises 3-6

3. When a person  sits on a chair, the stress that the chair has to withstand is due to the weight of the person, whereas the strength is the chair's ability to withstand the load without breaking. Indicate which is the strength and which is the stress in these two examples:

    A) A wardrobe hanting from a rope: Bending.

    B) A twisting telephone cord: Torsion.

6. Describe the structure of a turtle's shell. Why do you think it has this shape? What material do you think it is made from? Is it strong enough for the stresses it has to withstand?

The shell it's like an oval.
I thing that it is made of  a type of bone, an external eskeleton.

Yes I think it is cuse it has to withstand the turtle body.

7. Which types of stress do the following elements and activities have to support: 1) a rope with a weight hanting off it, 2) a man pushing a cabinet, 3) tightening a screw, 4) cutting our fingernails.

1) Bending

2) Compression

3) Tension

4) Shear

 9. Write s short description of three objects using one of the following adjectives for each object: rigid, elastic and plastic. Explain how these properties allow the objects to fulfil their function or make them suitable for yheir purpose.

Rigid: does not deform.

Elastic: deforms but then returns to its original shape.

Plastic: deforms and stays deformed.

Page 95, exercises 11-12

11. Copy and complete the following table in your notebook with objects that have the properties shown in the right-hand columm.

Object	Properties
Brick	Rigid
Plastic	Deformable
Rubber	Elastic
Plasticine	Plastic

12. Think about the following objects and state whether they are rigid, plastic or elastic: balloon, empty drinks can, window frame, clay, catapult, door.

Rigid: Door, Catapult.

Plastic: Balloon, Windows frame, Empty drinks can.

Elastic:  Balloon, Clay.