• demonstrate how pulleys work.

Activity

• Arrange the students in groups of four.

• Activity 1:
  
  1. Two students stand apart holding the ends of a
  round bar, such as a broom handle, at waist height.
  
  2. A small bucket of sand is placed on the floor below
  the middle of the bar. Each student should lift the bar
  to realize its weight.
  
  3. One student ties one end of the rope to the handle
  and loops the remainder of the rope over the bar.
  
  4. Another student will use the bar for a pulley as
  he/she hoists the bucket of sand.
  
  5. Have students take turns until all members of the
  group has had a turn hoisting the bucket.

• Activity 2:
  
  Repeat Activity 1, this time using a pulley attached to a
  board to lift the bucket of sand. Only differences this
  time, a length of board and pulley replaces the round
  bar.
  
  Discussion:
  1. What were the differences between the two
  activities?
  
  2. Which activity made it easier to lift the bucket?
  Explain.
  
  3. Did you have to work as hard or harder to lift the
  bucket using the pulley or was it easier without the
  pulley?
  
  Explain that they have just used a fixed pulley.

• Activity 3:
  
  Set up this activity like Activity 1, but this time have the
  end of the rope tied to the round bar. Loop the rope
  through the bucket handle (moveable pulley) and then
  over the top of the bar. Now pull on the rope to lift the
  bucket.
  
  Discussion:
  1. What were the differences between the three
  activities?
  
  2. Which activity made it easier to lift the bucket?
  Explain.

• You might also grow moulds from other materials, e.g., collect apple cores from recess snacks, and pieces of cheese. Have children look around and note any moulds they may have at home in their refrigerator or cupboard.

Assessment Tips from Old Tom the Turtle

• Circulate, observe, and ask questions as each child participates in the activities.

• Observe the child's social interactions with other class members.