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Impulse and momentum change calculator

Impulse J = F * delta_t (N*s) describes the effect of a force acting over time. It equals the change in momentum delta_p = m * delta_v. When a very large force acts briefly (impact, collision), impulse is more informative than force alone. The calculator computes J, delta_p and average force.

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How we calculate impulse

Formula: J = F * delta_t. Momentum change: delta_p = m * delta_v = J (impulse-momentum theorem). Average force: F_avg = delta_p / delta_t. Impulse is a vector – direction and sense match the force.

Example impulse calculation

A footballer kicks a ball (m = 0.43 kg). The foot exerts F = 1000 N for delta_t = 0.05 s. Impulse: J = 1000 * 0.05 = 50 N*s. Momentum change = 50 kg*m/s. Ball speed: delta_v = 50 / 0.43 ≈ 116 m/s.

Frequently asked questions about impulse and momentum

What is impulse of force?

Impulse J = F * delta_t (in N*s) is the product of force and the time over which it acts. It measures the cumulative effect of a force — important in collisions, shots and impacts where contact time is brief.

What is the impulse-momentum theorem?

The impulse-momentum theorem states that impulse equals change of momentum: J = delta_p = m * delta_v. Therefore F * delta_t = m * delta_v. It links the force-time product to the resulting change in motion.

What is momentum?

Momentum p = m * v (kg*m/s) is the product of mass and velocity. It is a vector quantity. The total momentum of an isolated system is conserved (law of conservation of momentum).

For a given impulse J, F = J / delta_t. Shorter contact time means greater average force. Airbags extend collision time to reduce the peak force on the driver for the same overall impulse.

In a system with no external forces, total momentum is constant. Collision of two balls: m1*v1 + m2*v2 = const. Fundamental in mechanics, astrophysics and nuclear physics.

Force F (N) is the instantaneous interaction. Impulse J = F * delta_t accounts for both magnitude and duration. Two force-time combinations can give the same impulse: 100 N for 1 s = 50 N for 2 s.

For a constant force J = F * delta_t. For a time-varying force J = integral of F(t) dt from t1 to t2. As an approximation, use average force: J = F_avg * delta_t.

In quantum mechanics momentum is an operator: p = -i*hbar*(d/dx). Heisenberg's uncertainty principle states delta_x * delta_p >= hbar/2. This is distinct from classical momentum m*v.

Kicking (football, tennis, baseball): force F and contact time delta_t (typically 1–50 ms) are measured. High force over short contact gives large impulse and ball speed. High-speed video allows precise measurement of both.

Impulse J = F * delta_t (N*s) involves force and time; its result is a change of momentum. Work W = F * delta_s (J) involves force and displacement; its result is a change of kinetic energy. They are distinct physical quantities.

Calculator results are for educational and informational purposes only.

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Impulse and momentum change50 N·sImpulse J (N·s)
Momentum change (kg·m/s)
50 kg·m/s
Average force F_avg (N)
0 N