Invisible Forces

Why do hoppers hop off the table and into the air?

• The students make them hop.

• The rubber band is stretched and then pulls on the sides of the cardboard when released.

• The ruler makes them hop off the table.

Why are pillar and arch bridges stronger than board bridges?

• The force of people and cars push down on bridges.

• Pillar and arch bridges have support underneath.

• The board bridge does not have any support under it.

• All of these are correct.

If you want to go down a slide faster, what can you do? Select all correct answers.

• Wear something bumpy

• Wear something slippery

• Put a slippery material underneath you

• Make the slide more slippery

Are paper clips magnets?

• Yes of course.

• No, but they can become magnetized for a little while after coming in contact with magnets.

• Yes because they stick to magnets.

In the video clip, why was it hard to win Tug-of-War against teachers?

• The students were slippery.

• The teachers had more legs than the students.

• The teachers had more friction from pushing than the students.

The last rubber band caused the watermelon to burst because...

• It finally had a greater force than the watermelon rind.

• It was stronger than the other rubber bands.

• It was thicker than the other rubber bands.

Why was a suspension bridge a good design for the Golden Gate Bridge?

• It had a lot of pillars.

• The distance that the bridge had to go across wasn't very long.

• The water under the bridge was shallow.

• Ships had to travel under the bridge.

Sandpaper sliders don’t slide very fast because....

• sand makes the slider too heavy.

• sandpaper is too rough and causes too much friction.

• it didn’t have enough pennies on it.

• the slide isn’t long enough.

Magnets attract....

• Anything made of metal.

• Only other magnets.

• Objects made of iron.

• Things that aren't too heavy.