Example 1
F = 100 N, Δt = 0.5 s → J = 50 N·s.
Impulse calculator
Pick a mode: F·Δt or change of momentum. 100 N for 0.5 s is 50 N·s. 1000 kg from 20 m/s to 0 is 20,000 kg·m/s. J and Δp share the same unit.
p = m v alone: momentum. Braking: decelerated motion.
Result
Calculation mode, Force F, Time Δt (s) and Mass / vₖ (mode-dependent). The result shows up here.
How it works
Impulse J = F Δt equals the change of momentum Δp = m(vₖ - v₀). 100 N for 0.5 s: J = 50 N·s. 400 N for 0.02 s on a ball: J = 8 N·s. 50 N for 0.15 s: J = 7.5 N·s. 200 N for 1.2 s: J = 240 N·s. 1000 N for 0.5 s: J = 500 N·s. N·s and kg·m/s are the same unit: 1 N·s = 1 kg·m/s.
A 1000 kg car from 20 m/s to rest: Δp = 1000 × (0 - 20) = -20,000 kg·m/s, magnitude 20,000 to stop. 800 kg from 0 to 2 m/s: Δp = 1600 kg·m/s. 20,000 kg from 10 m/s to 2 m/s: Δp = -160,000 kg·m/s. 80 kg from 8 m/s to 3 m/s: Δp = -400 kg·m/s. The sign says whether momentum rises or falls.
Mode F·Δt: fields F and Δt. Mode change of momentum: m, v₀, vₖ. The required fields of the mode need a number. Typed Δt = 0 gives J = 0. A comma and a period are the same time: 0,5 and 0.5. Pick a mode before you click Calculate: the calculator does not guess whether you know F or the speeds.
p = m v alone is on the neighbouring page. Here it is the change of that momentum or F times time. Stopping distance and decelerated motion give s and t, not J. 14 m/s and 7 m/s² is 14 m and 2 s, but impulse you compute from F Δt or from m Δv.
Mean F from J / Δt is the inverse of F·Δt mode. If you know J = 50 N·s and Δt = 0.5 s, F = 100 N. This calculator does not plot F(t): it takes a constant F or a constant change in v.
Pick F·Δt, type 100 and 0.5, click Calculate, and match 50 N·s. Then Δp mode: 1000, 20, and 0. The header symbol does not kick the ball.
How to use
- Pick a mode: F · Δt when you know force and time, or change of momentum when you know m, v₀, and vₖ.
- In F·Δt type 100 N and 0.5 s. Result 50 N·s. 400 N for 0.02 s gives 8 N·s.
- In Δp type m, v₀, and vₖ, for example 1000 kg, 20 m/s, 0. Result 20,000 kg·m/s to stop.
- Click Calculate. N·s and kg·m/s are the same unit. The sign of Δp is the direction of the change.
- For p = m v alone, open momentum. Stop distance is on decelerated motion.
Formula
J = F·Δt
J = Δp = m(vk − v0)
Unit: N·s = kg·m/s.
J, Δt, and Δp in a force impulse
Impulse here has two modes: J = F·Δt or J = Δp = m(vₖ − v₀). Unit N·s = kg·m/s. Not the rest momentum m v at one instant.
- J
- Impulse, the result. At F = 200 N and Δt = 0.1 s, J = 20 N·s. In momentum mode J = m(vₖ − v₀).
- F
- Force in F·Δt mode. Average |F| also appears when you compute from Δp and know Δt.
- Δt
- Duration of the force, in seconds. Zero does not divide when you go back to F = J/Δt.
- Δp
- Momentum change, equal to J. 2 kg from 3 m/s to 8 m/s is Δp = 10 kg·m/s.
- v₀
- Speed before the impulse, momentum mode. Leave blank when you compute from F and Δt.
- vₖ
- Speed after the impulse. With v₀ and m it gives J without typing F.
Real-life examples
Example 2
m = 1000 kg, v₀ = 20 m/s → 0.
Example 3
F ≈ 400 N for 0.02 s on the ball.
Example 4
m = 800 kg, v₀ = 0 → 2 m/s.
Example 5
F = 50 N, Δt = 0.15 s.
Example 6
m = 20000 kg, 10 m/s → 2 m/s.
Example 7
F = 200 N for 1.2 s.
Example 8
m = 80 kg, 8 m/s → 3 m/s.
Example 9
F = 1000 N, Δt = 0.05 s.
Ways to use this calculator
- You compute a kick: 400 N for 0.02 s.
- You check Δp of a 1000 kg car from 20 m/s to rest.
Frequently asked questions
How much J at 100 N and 0.5 s?
J = 100 × 0.5 = 50 N·s. At 400 N and 0.02 s that is 8 N·s. At 200 N and 1.2 s that is 240 N·s.
How much Δp at 1000 kg from 20 m/s to 0?
Δp = 1000 × (0 - 20) = -20,000 kg·m/s. Magnitude 20,000 kg·m/s to stop.
Which units do I type?
F in newtons, Δt in seconds, m in kg, v in m/s. J in N·s. 1 N·s = 1 kg·m/s.
Which mode should I pick?
You know F and time: F·Δt. You know m and speeds: change of momentum. The calculator does not guess the mode.
How is this different from momentum?
Momentum is m v. Impulse is the change of that momentum, or F Δt. 70 kg at 1.4 m/s is 98 kg·m/s, with no Δt.
Is N·s the same as kg·m/s?
Yes. 1 N·s = 1 kg·m/s. That is why J and Δp share a unit.
How much at 800 kg from 0 to 2 m/s?
Δp = 1600 kg·m/s. At 80 kg from 8 m/s to 3 m/s that is -400 kg·m/s.
Does a comma in 0.5 work?
Yes. 0,5 and 0.5 are the same Δt. A comma and a period mean the same value.
Where is stopping distance?
On decelerated motion or stopping distance. Here J, not s. 14 m/s and 7 m/s² is 14 m and 2 s.
How much at 20,000 kg from 10 m/s to 2 m/s?
Δp = -160,000 kg·m/s. At 50 N and 0.15 s, J = 7.5 N·s.
Knowledge sources
The formula is the school one. Units follow SI; NIST SP 330 and BIPM define the measures, not your result.
Page updated in 2026.