Two identical 1.0-kg toy cars move at 3.0 m/s, one due north and the other due west. The total momentum of the system is
A) 0 N.s.
B) 3.0 N.s, NW.
C) 4.2 N.s, NW.
D) 6.0 N.s, NW.
E) 18.0 N.s, NW.

Question

Quizplus · Accepted Answer

The total momentum is found by combining the momenta of the two cars vectorially. Each car has a momentum of $1.0 \, \text{kg} \times 3.0 \, \text{m/s} = 3.0 \, \text{N.s}$. Since they are perpendicular to each other, use the Pythagorean theorem to find the resultant: $\sqrt{(3.0)^2 + (3.0)^2} = \sqrt{18} = 4.2 \, \text{N.s}$, and the direction is northwest (NW) because the momenta are equal and perpendicular.

Two Identical 1