Which reduces friction more: #40 oil, #10 oil, or an edible oil?
4 pieces of wood, 25 cm long x 8 cm wide and 2 cm thick, one side smooth (Make sure all 4 blocks are the same size!)
4 blocks of wood, 6 cm x 6 cm x 4 cm, edges should be saw-cut, not sanded (These 4 should all be the same size, too!
Do this first:
Coat one side of the boards and blocks with very thin layers of oil. Rub them down with paper towels. Don't leave any extra oil on them!
Raise the board to make an inclined plane. Drop the block gently onto the board at bigger and bigger angles until the block slides quickly downhill. Record the angle at which the block slides best.
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