Invisible Forces Assessment

Why do hoppers hop off the table?

• Hoppers hop off the table because of the rubber band. 
• Hoppers hop off the table because of the cardboard.
• Hoppers hop off the table because the hopper is flat.
• Hoppers hop off the table because of the push.

Why are pillar bridges and arch bridges stronger than board bridges?
                                                                             

• Board bridges have a lot of structure.
• The force of people and cars pushes down on bridges.  Pillars and arches push up from below to balance the downward push.
• Board bridges are made of structurally sound materials.
• The push and pull on a pillar bridge is similar to the forces of a board bridge.

Which bridge is the strongest?

• Pillar
• Arch
• Board
• Pillar and arch

Why is it hard to win a tug-0-war against an elephant?

• Elephants try really hard
• Elephants have more legs than we do
• Elephants have a lot of friction
• Elephants can push really hard

The last rubber band caused the watermelon to burst because ________?

• It was stronger than all of the other rubber bands? 
• It was thicker than the other rubber bands
• It was the last rubber band in the bag
• It created a force that was greater than the force of the watermelon rind

When you look at a smooth surface under a powerful microscope, what does it look like?  (Think of the sandpaper when we made slides)

• It looks completely smooth. 
• It might have a few bumps, but it mostly looks really smooth.
• It looks smooth and wavy.
• It looks really jaggedy.

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

• Ships had to pass underneath the bridge.
• It has a lot of pillars underneath to support it.
• The distance the bridge had to cross wasn't very long.
• The water under the bridge was very shallow.

Sandpaper sliders don't slide very fast because _______

• sand makes the slider too heavy
• sandpaper creates a lot of friction
• it didn't have enough pennies on it
• the slide isn't long enough

Magnets attract

• objects that contain iron
• only other magnets
• anything made of metal
• things that are not too heavy

The opposite sides of magnets are called

• North and south poles
• East and west poles
• Top and bottom
• attract and repel