A 4.00 kg ball is moving at 4.0 m/s to the right and a 6.00 kg ball is moving at 3.00 m/s to the left. The total momentum of the system is
A) 16 kg m/s to the right.
B) 2.0 kg m/s to the right.
C) 2.0 kg m/s to the left.
D) 18 kg m/s to the left.
E) 34 kg m/s to the left.

Question

Quizplus · Accepted Answer

Momentum is a vector quantity, meaning it has both magnitude and direction. To find the total momentum of the system, we need to add the momenta of the individual objects.
Let's define rightward as the positive direction and leftward as the negative direction. Then, the momentum of the 4.00 kg ball is:
p1 = m1v1 = (4.00 kg)(4.0 m/s) = 16.0 kg m/s to the right 
And the momentum of the 6.00 kg ball is:
p2 = m2v2 = (6.00 kg)(-3.0 m/s) = -18.0 kg m/s to the left
Notice that we use a negative sign for the velocity of the 6.00 kg ball because it is moving to the left.
To find the total momentum, we add these two momenta:
ptotal = p1 + p2 = 16.0 kg m/s to the right + (-18.0 kg m/s to the left)
Simplifying this expression, we get:
ptotal = -2.0 kg m/s to the left 
Therefore, the best choice is C) 2.0 kg m/s to the left.

A 400 Kg Ball Is Moving at 4