How this calculator works
The pendulum loses gravitational potential energy between release and rebound. Subtract an independently measured friction and windage correction to estimate specimen absorption. Angles are measured from the downward vertical, and the radius refers to the effective mass-centre lever arm in this point-mass model. A real impact machine uses its calibrated pendulum moment and instrument-specific corrections. The ideal impact-speed estimate neglects approach losses. This page supports energy accounting and does not certify a Charpy test.
Formula
h = R(1-cos beta); h1 = R(1-cos alpha); E_abs = m g (h-h1) - E_loss; ideal v = sqrt(2gh).
Worked example
For m = 10 kg, g = 10 m/s2, release height 1 m, rise height 0.4 m and 2 J correction, absorbed energy is 58 J and ideal impact speed is 4.47214 m/s.
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Frequently asked questions
Is the entered mass the stationary anvil?
No. It is the effective pendulum mass for the chosen mass-centre radius. The stationary support mass is not part of this energy formula.
Can I ignore friction?
Only if it is negligible for your purpose. Calibrated test procedures apply machine-specific energy corrections.
Can a larger rise angle absorb more energy?
For the same release, a larger rebound height means more energy remains in the pendulum and less was absorbed.