• Question: Why does the metal get hotter when you cut it?

    Asked by ✘Jakub216✘ to Andrew, Angela, Eleanor, Emma, Withdrawn on 7 Mar 2016.
    • Photo: Andrew Pidgeon

      Andrew Pidgeon answered on 7 Mar 2016:

      It gets hot because friction causes the surfaces to heat up.

      An example to prove this is to put your hands together and start rubbing them slowly. There is not much heat.

      However rub them really fast and you will feel the heat being generated!

      In engineering we can reduce this heat by using oil or water to cool down or lubricate the objects.

      Rub your hands really fast in cold water and the don’t get as warm!!

    • Photo: Eleanor Sherwen

      Eleanor Sherwen answered on 8 Mar 2016:

      If you look at the saw, you can see it’s made of lots of little triangle teeth. When you “cut” the metal, you are rubbing the little teeth over it to break off little pieces and wear bits away. That means you are using friction in cutting. Friction makes heat (see physics note) and you rub the saw over lots and lots of times, making lots of heat, which gradually spreads out through the metal and makes the bit near your hand feel hotter.

      physics note: Friction makes materials hot because rubbing one surface over another stretches the bonds between atoms in the surfaces. When the surfaces aren’t in touch any more, the atoms spring back, releasing energy as heat.

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