Impact Force Calculator

How it works

1. 1Enter the object’s mass, its velocity just before impact (u), its final velocity (v, usually 0 for a full stop), and the contact time.
2. 2The calculator finds the change in momentum Δp = m·(u − v) using the impulse–momentum theorem.
3. 3It divides Δp by the contact time to give the average impact force F = Δp ÷ Δt, in newtons or pound-force.

Use cases

• Estimating the force on a car occupant in a collision to assess airbag and crumple-zone effect.
• Calculating the load on a sports helmet as an athlete’s head decelerates.
• Determining the force in a drop-test rig when a package hits a surface at a known speed.

Frequently asked questions

What formula does this calculator use?

Newton’s second law in impulse form: F = Δp ÷ Δt, where Δp = m·(u − v). A 70 kg object at 10 m/s stopping (v = 0) in 0.1 s has Δp = 700 kg·m/s and an average force of 700 ÷ 0.1 = 7000 N.

Why does a longer contact time produce a smaller force?

Force equals the fixed momentum change divided by the contact time: F = Δp ÷ Δt, so doubling t halves F. That is why crumple zones, airbags, and padded helmets work — they extend the stopping time and lower the peak force.

When should the final velocity v be non-zero?

When the object does not fully stop — a ball that bounces off a wall and leaves slower, or vehicles that collide and keep moving. The momentum change is still m·(u − v).