- Does the completed arch seem strong or stable to you?
The completed arch does NOT seem very strong or
stable, but there is a hidden strength in it. If a string was carefully
laid over the top of the arch, the arch will withstand a surprisingly
strong, gentle pull on the string ends.
- What happens when you dont put the blocks in numerical order?
When the blocks are not in order, they do not
form the arch shape. (Each block has a slightly different angle cut
on the top and bottom so the higher blocks tilt in more.)
- Instead of an arch, try building a tower. Draw what it looks like.
Drawings may vary. Here are two possible results.
- Which beam supports your weight better?
The beam with the longer edge vertical, not horizontal.
- Pick up both beams and switch their places so the beam that was lying
flat is now on its side. Which beam supports your weight better now?
Again, the beam with the longer edge vertical,
not horizontal. (The way the beam is placed makes the difference, not
the beam itself.)
- How are the two beams different?
One is thinner and taller; one is wider and shorter.
- Draw what happens when someone stands in the middle of a beam.
- Draw what happens when someone stands near the end of a beam.
- Can you get the entire block to stick out beyond the length of the
bottom block? Draw it.
Notice that you can slide the weight up and down.
When is the stick easier to balancewith the weight
high or the weight low?
Though you might think it's easier to balance with
the weight lower, it's actually easier with the weight higher. This is
because the weight is further from the pivot point, and so it falls more
slowly. This quality of "angular momentum" is similar to why a figure
skater slows down as he/she extends his/her body outward from the axis
of their spin.
- Do your hands move smoothly together, or with stops and starts?
Stops and starts. This is because the weight over
each hand is constantly changing as both move toward the center. More
weight (mass X gravity) on one side means more friction needs to be
overcome, and so the stop. When there is more weight on the other side,
it starts again.
- When your hands come together, are you balancing the stick?
- What do you think makes one hand stop while the other keeps moving?
Friction causes one hand to stop moving. The force
of friction increases as the weight of an object increases, so when
you feel one side of the stick get heavier, the increased friction stops
the movement of that hand.
- Try it with two people (using one hand each). What happens?
Should still work.