Wheels and axles.

    The first conveyances were probably trails.

A trail can increase propulsion.

     But some clever men  made trails by putting  rolling logs under it. 

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Do the rolls help ?

You need a cardboard , some rubber,a match, some tape,stones,a ruler and some rotund pencils. 

1. Make a hole in the box and fix the rubber with a match and tape.
2.  Put some stones into the box and try to drag.
4. Measure  the length of the  rubber .
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5. Put pencils under the box and drag again.6. Measure  the length of the  rubber  again.

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What did you notice?

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7. What forces impede the draggling?
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8. Are rolls better than trails?
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   From rolls wheels and axles were invented.     Friction force is smaller when a wheeler rolls..

Friction is a resistance force that occurs between 2 surfaces as they move across each other
1. What would be different when there's no wheels?

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