Science - Structures and Machines

Unit 6 - Structures and Machines

1 - Structures:

WHAT IS A STRUCTURE?

A structure is a group of elements wich can support lots of weight or can protect objects and machines they belong to

the structures can be:

• natural : f.e. the skeleton 
• artificial : f.e. bridges, lever etc

WHAT IS A BRIDGE?

A bridge is a structure that can support very large forces.
They can support:

• their own weight
• the movements caused by the wind

PUENTE DE LISBOA

Types of bridges:

• Arches: the stones form a curved arch
• Girder: we join triangular pieces so we can make long and resistant bridges this way.

 2 - Simple machines:

A simple machine help us reduce the force for doing something.

TYPES

• LEVER: Is a rigid bar wich is balancedon a point called fulcrum (FU). We transmit a force (f) and we move the load (l) that is on the other part

• WHEEL: Circular object that rotates around a central axle.
• INCLINED PLANE: Is a flat surface with one edge raise higher than the other or a ramp wich we can use to rase or lower object with less force.
• SCREW:  If we roll an inclined plane round  a cylinder or axis we make a screw
• WEDGE:  We can have a wedge with the join of two inclined planes.
• PULLEY:  Is a wheel with a channel wich guides a rope. When we pull the rope the object rase.
• THE HUMAN BODY:  The human body has three classes of levers.
1. When the fulcrum is between the force and the load(head)
2. When the load is between the fulcrum and the force (foot)
3. when teh force is between the fulcrum and the load(arm)
• Prueba estos juegos.