Tecnology Unit 5

Tecnology Unit 5

1. Structure

   • structure of an object
     • Orderly distribution of essential parts. It gives the object shape
   • Is a collection of elements that support body or object
   • Types
     • Mass
       • walls, dams
     • Frame
       • structure of a building
     • Truss
       • cranes, electricity pylons
     • Suspended
       • suspesion bridges, tents, marquees
   • Force
     • influence deform body or change its movement
   • Stresses
     • phisical demands that a body or object must withsand becauseof an externa applied force
     • Types
       • Tension
         • Suspension bridges, towbars, crane cables
       • Compession
         • columns, uprights of a bunk bed, the legs of chairs
       • Shear
         • scissors, die-cutting, ends of beams
       • Bending
         • plataform bridge, book case, aeroplane wing
       • Torsion
         • screw, axes of machines
   • Strength
     • its the ability to withstand external forces without breaking

2. Simple Machines

   • Levers
     • Simple machines, rigid bar, point of support, fulcrum
     • F.L =R.L
     • First class
       • Seesaw
     • Second class
       • Wheelbarrow
     • Third class
       • Fishing rod
   • Cams
     • rotational motion into reciprocating linear motion
     • Operate a toy, connect and disconnect a circuit, rev counter
   • Pulleys
     • lift heavy loads. Wheels (grooved rim)
     • Types
       • fixed
       • moveable
   • Friction Wheels
     • water wheels, record players, electronic equipment
   • Worm gear
     • allows rotational movement to be transmitted between two perpendicular axes
     • Conveyor belt, opening and closing of hydraulic valve