How this calculator works
Classical linear momentum is mass times velocity, so it points in the velocity direction. Apply the relation independently to each Cartesian axis. The vector magnitude is always nonnegative, whereas a component can be negative. This model assumes constant mass and speeds small compared with light speed. Momentum belongs to a reference frame; changing frames changes its value.
Formula
p = mv; (px,py,pz) = m(vx,vy,vz); |p| = sqrt(px^2+py^2+pz^2).
Worked example
A 2 kg body moving at -3 m/s has momentum -6 kg m/s. With velocity (3,4,0) m/s, its momentum is (6,8,0) kg m/s and magnitude is 10 kg m/s.
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Frequently asked questions
Why can momentum be negative?
The sign identifies direction along your chosen axis.
Is momentum the same as kinetic energy?
No. Momentum is a vector proportional to velocity; kinetic energy is a scalar proportional to speed squared.
Do the vector entries need a common frame?
Yes. Use the same origin orientation, reference frame and measurement time for all components.