momentum
definition
momentum is mass multiplied by velocity. p = mv (unit: kgm/s). heavier or faster objects have greater momentum.
impulse and force
impulse is the change in momentum: impulse = f∆t = ∆(mv). applying a large force briefly gives same impulse as small force over long time. this is why seatbelts in cars increase the time of impact, reducing force and injury.
conservation of momentum
in collisions and explosions with no external forces, total momentum is conserved. momentum before = momentum after. applies to two objects colliding or separating.
formula: m1u1 + m2u2 = m1v1 + m2v2, where u1 and u2 are initial velocities and v1 and v2 are final velocities, and m1 and m2 are the masses of the objects.
resultant force and momentum
resultant force equals the rate of change of momentum: f = ∆p / ∆t. a larger force produces faster change in momentum.
momentum
the product of mass and velocity. p = mv (unit: kg·m/s). a measure of how difficult it is to stop a moving object.
impulse
the change in momentum caused by a force. impulse = f∆t = ∆(mv) (unit: ns or kgm/s). a large force over short time can equal a small force over long time.
conservation of momentum
in a closed system with no external forces, total momentum before = total momentum after, or m1u1 + m2u2 = m1v1 + m2v2. applies to collisions.
force from momentum
the rate of change of momentum. f = ∆p / ∆t force measures how quickly momentum changes.