Week3

• Pulley


  • is a variation of a wheel and axle. Instead of an axle, a rope moves along a wheel with the groove. A
  • groove
  • is a long, narrow channel that keeps the rope or cord on the wheel in place. One rotation of the wheel makes the rope move up in one direction and down on the other side.
• Pulley


  • It is used to lift the load, put it down, or move sideways. A pulley multiplies the force applied
  • to it.
• Imagine you are in a ship sailing in the ocean. What examples of pulley can be seen there? What will happen if there is no pulley used in there?
• How do pulleys work?

  When one other end of the rope is pulled down the other end where the load is attached goes up. This only shows that pulley changes the direction of the force. The amount of force you apply on the rope is equal to the weight or the amount of force acting on an object.
• Imagine having only these two materials, how do you think you can create a pulley out of them?
• The greater the mass of an object, the "heavier" it becomes due to the pull of gravity acting on it. Also, the distance that the rope covers as you pull it is similar to the distance of the object that you have lifted. For instance, if you pulled a rope 1 meter long, the load will be lifted 1 meter high from the ground.
• How do pulleys work?

  1. When there are more pulleys working together, less effort is applied to the rope in order to lift the load. However, more pulleys require greater distance in terms of pulling the rope.

  2. Suppose that 1 meter is looped around each grooved wheel. To lift the object 1 meter high, the rope will have to be pulled 3 meters since it is looped around 3 grooved wheels.
• Classification of Pulleys


  • fixed
  • movable
  • compound
• Fixed pulley


  the wheel is attached to an immovable support. Only the rope moves along the grooved wheel and the wheel remains in its position.
• A fixed pulley may just be a single pulley or multiple grooved wheels. In order to lift the load in a fixed pulley, the force applied should be equal to the weight of the load.
• Movable pulley


  has a wheel and rope that moves along with the load. One end of the rope is attached to a fixed support while the grooved wheel moves along the rope. In this pulley, the load moves in the same direction as the effort.
• Similar to a fixed pulley, it can be made of single or multiple wheels. But unlike in the fixed pulley, the effort applied in a movable pulley is less than the weight of the load. However, the effort still depends on the length of the rope and the number of grooved wheels.
• Compound pulley


  is also known as a combination pulley because it contains fixed and movable pulley. This kind of pulley is often used to carry heavy loads.
• The more grooved wheels and supporting rope are present in a compound pulley, the lesser force is exerted to lift a heavy object.
• How do you think pulleys are used in the past?
• How would you finally describe pulleys using the picture below?
• Let us check your hypotheses!
• Let us observe!
• Simple machines may be categorized into two major groups.
• Lever


  • is a bar or a rigid arm that turns on a fixed point.
  • It's used to lift a heavy object with less amount of force.
• Seesaw is an example of a lever.
• The basic parts of a lever are:

  • fulcrum
  • - fixed point where the bar turns
  • effort
  • - effort applied to the lever
  • load
  • - force that the lever needs to overcome
• The distance between the fulcrum and the effort is known as the

  effort arm
• First-class Lever


  • the fulcrum is between the effort and load.
  • This class of lever changes the direction of force.
• First-class Lever


  Before lifting the load (A), less amount of force is applied to the effort arm but the force is exerted over a tall height. The load arm lifted the load but only for a short height (B).
• Examples of First-class Lever


  • claw hammer
  • crowbar
  • pliers
• Second-class Lever


  • the load is in between the effort and fulcrum.
  • In this type of lever, the load moves in the same direction of the applied force.
• Second-class Lever


  The closer the load is to the fulcrum, the less force is applied to move the load in the second class lever.
• Examples of Second-class Lever

  • wheelbarrow
  • nutcracker
  • car door
• Third-class Lever


  • the effort in between the load and fulcrum.
  • In this kind of lever, the force applied is always greater than the load.
• Third-class Lever


  In third class lever, the force is applied in between the fulcrum and the load.
• Examples of Third-class Lever


  • human arm
  • tong
  • fishing rod