Student #1

Materials:

• Wig-wag
• Various block weights

This piece of apparatus is sometimes called a "wig-wag."

Push the end sideways a few centimeters and let it go.

Now put the block with the red sticker on it into the tray and push it sideways again.

1. What difference does putting the block into the tray make to the way the "wig-wag" moves?
   
   
2. Now try each of the other blocks and say what you notice about the effect the blocks have on the way the "wig-wag" moves.
   

Discussion

In part (a) pupils seldom refer to more than one property of the balance in motion, as is evident from the response given.

This feature is common to many observation questions focusing on events or relationships. Pupils are happy to note one observation when there are several of relevance to a scientist.

In part (b) the blue block had the greatest mass, and the yellow block the least. Again pupils concentrate on just one property of the balance changing with the mass of the block in the tray. A large number note a change, but as in the first response below, do not comment on the relationship between changing mass and aspects of motion. The second illustrates a response in which the particular values are translated into a general relationship.