David Lang wrote:

I used to have one, very useful bit of kit with a 4lb lump hammer behind it.
How many Joules would that be?

Depends on how hard you hammer!

Lets say you stick 100N of force onto the hammer. That gives you a
hammer acceleration of 100 / 1.8 = 55 m/s^2

Over a 20cm stroke length that will get you to an impact speed of
sqrt( 2 * 55 * 0.2 ) = 4.7 m/s

energy = 0.5 * 1.8 * 22 = 20J

So quite a bit then!


--
Cheers,

John.

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