How this calculator works
Stopping removes the initial translational kinetic energy. Work gives a force averaged over distance; impulse gives a force averaged over time. They agree for the constant or symmetric triangular stopping histories offered here. A triangular pulse starts and ends at zero force and has twice the average as its peak. Real impacts can have a different peak and pulse shape.
Formula
E = mv^2/2; F_distance = E/d; F_time = mv/t. Constant or symmetric triangular stop: d = vt/2. Triangular peak = 2 F_time.
Worked example
A 10 kg mass at 5 m/s carries 125 J. Stopping over 0.1 m gives an average 1250 N. Stopping over 0.04 s gives the same average; a triangular pulse peaks at 2500 N.
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Frequently asked questions
Is the peak force measured by this calculation?
No. It is inferred from the pulse model you select. Energy and distance alone cannot determine the real peak.
Does this include gravity during a vertical impact?
No. The result is the net decelerating force magnitude. A supporting contact force can also include weight.
What final speed is assumed?
Zero. For a rebound or a nonzero final speed, energy and impulse changes need a different model.