Answer: 3.75 m/s
Explanation:
Here's what you know: The car has mass 1500 kg, and initial velocity 15.0 m/s. The truck has mass 4500 kg and initial velocity 0 m/s. The final mass is 6000 kg (4500 kg plus 1500 kg, because they stick together) and we are looking for the final velocity. Using the formula p = mv, and the concept that p before equals p after, the p of the car plus p of the truck equals the p of them together. So, 1500 x 15 + 4500 x 0 = 6000 x v final. 22500 = 6000 v, and v = 3.75 m/s. The velocity is positive, and the initial velocity of the car was positive, so the two vehicles together are traveling to the south just like the car was initially.
