An 80-kg football player travels to the right at 8 m/s and a 120-kg player on the opposite team travels to the left at 4.0 m/s. The total momentum is
A) 240 kg m/s to the left.
B) 160 kg m/s to the right.
C) zero.
D) 160 kg m/s to the left.
E) 1120 kg m/s to the right.

Question

Quizplus · Accepted Answer

The total momentum can be calculated by adding the momentum of each player, taking direction into account. The momentum of the first player is $80\,kg \times 8\,m/s = 640\,kg\,m/s$ to the right, and the momentum of the second player is $120\,kg \times 4\,m/s = 480\,kg\,m/s$ to the left. Converting the second momentum to the right direction for addition gives $-480\,kg\,m/s$. Adding these together, $640\,kg\,m/s - 480\,kg\,m/s = 160\,kg\,m/s$ to the right.

An 80-Kg Football Player Travels to the Right at 8