total momentum prob.?

Question

A 5.0 kg ball is moving at 4.0 m/s to the right and 6.0 kg ball is moving at 3.0 m/s to the left. The total momentum of the system is??

please help, thanks!

Answer 1

The total momentum of the system can be found as the vector sum of all of the individual momentums of each component of the system.
Finding the momentum for each ball, then adding them all together.

Momentum = mass * veloccity

Ball 1:
P_1 = m_1 * v_1
P_1 = (5.0 kg) * (4.0 m/s to the right)
P_1 = 20 kg m/s to the right

Ball 2:
P_2 = m_2 * v_2
P_2 = (6.0 kg) * (3.0 m/s to the left)
P_2 = 18 kg m/s to the left

The momentum vectors of each ball are along the same axis (they both point along the left-right axis), even though they act in opposite directions. To make it easier to add these two quantities we can assume the “right” direction as being positive and the “left” direction as being negative, then we can write the momentums as,
P_1 = +20 kg m/s
P_2 = -18 kg m/s

Now we add these momentums together,
P_total = P_1 + P_2
P_total = +20 kg m/s – 18 kg m/2
P_total = +2 kg m/s

Since + is in the right direction, the total momentum of the system is,
P_total = 2 kg m/s to the right