Science Puzzle Answers

by John P. Pratt
last updated 24 Nov 2001

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  1. A barge with one man and a load of iron scrap is on a barge floating in a lock in the Panama Canal. If the man throws some iron off the barge into the water, what will happen to the water level on the side of the lock? While the iron was floating, it displaced and amount of water equal to its weight, which is about five times its volume. When thrown into the water it only displaces its volume. Thus, after being thrown into the water, the water level on the side of the lock goes DOWN slightly.

  2. A van with all the windows closed contains some helium-filled balloons floating in it. When it starts accelerating what happens to the balloons? The accelerating van pushes on the air which supports the balloons. Since the balloons are lighter than air they are accelerated towards the front of the van. Try this it an see.

  3. A van containing pigeons on perches is being weighed on a scale. Something scares the pigeons and they all begin flying around inside the van. Does the total weight of the van and pigeons change? No it doesn't because the birds were being supported by the van before and by the air within it after, so it both cases the weight is equal to the sum of that of the van plus the pigeons.