Kelly is driving a car with a mass of 800 kilograms in a south direction with a speed of 18 meters/second. dominic is driving a truck with a mass of 1500 kilograms with a velocity of 15 meters/second to the east. they undergo perfectly inelastic collision. what is the magnitude of the final momentum of both the truck and the car.

We are given
m1 = 800 kg
v1 = 18 m/s south

m2 = 1500 kg
v2 = 15 m/s east

using the momentum balance for perfectly inelastic collision
along the x:
m1v1 + m2v2 = (m1 + m2) vx
0 + 1500 (15) = (800 + 1500) vx
vx = 9.78 m/s

along the y:
800 (-18) + 0 = (m1 + m2) vy
vy = -6.26 m/s

the magnitude is
v =  √(vx² + vy²)
v =  √( 9.78² + (-6.26)² )
v = 11.61 m/s

Is a  vector quantity  that refers to "the rate at which an object changes its position." imagine a person moving rapidly - one step forward and one step back - always returning to the original starting position. while this might result in a frenzy of activity, it would result in a zero velocity. because the person always returns to the original position, the motion would never result in a change in position. since velocity is defined as the rate at which the position changes, this motion results in zero velocity. if a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. every step must go into moving that person further from where he or she started. for certain, the person should never change directions and begin to return to the starting position.