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Linear momentum
Beginner
The product of mass and velocity.
p = mvMomentum p = mv combines how much matter moves with how fast. It is a vector pointing along the velocity, in kg·m/s, and is what a collision exchanges.
A 0.16 kg ball at 30 m/s has p = 4.8 kg·m/s.
Momentum is not energy; two bodies with equal momentum can have very different kinetic energy.
In more detail
Linear momentum is the product of mass and velocity, p = mv. A heavy slow object and a light fast one can have the same momentum.
Real-world uses
- Stopping a heavy lorry requires a larger impulse than stopping a bicycle at the same speed.
- Ball sports coaches teach players to follow through to change a ball's momentum smoothly.
- A heavy lorry and a small car moving at the same speed have very different momenta, which decides how hard a collision will be.
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Frequently asked questions
Is momentum the same as kinetic energy?
No. Momentum is a vector linear in velocity, while kinetic energy is a scalar that depends on speed squared.
Can an object have zero momentum and still move?
No. If it moves, its momentum is non-zero, since mass is positive.
Is momentum the same as force?
No. Momentum is mass times velocity, a property of a moving body, while force is the rate at which momentum changes.