1. The problem statement, all variables and given/known data Two cars collide at an intersection. Car A, with mass 2000 kg, is going from west to east, while car B, with mass 1500 kg, is going from north to south at 15 m/s. As a result of this collision, the two cars become enmeshed and move as one afterward. In your role as an expert witness, you inspect the scene and determine that, after the collision, the enmeshed cars moved at an angle of 65° south of east from the point of impact. How fast were the enmeshed cars moving just after the collision? 2. Relevant equations I use the law of conservation of momentum (p1 = p2 in both the x- and y-direction. 3. The attempt at a solution First I try to find the momentum in the x-direction with the equation p1x = p2x. I insert the values from the problem statement: x-dir: 2000 kg * vA1x + 1500 kg * 0 m/s = (2000 kg + 1500 kg) * vABx * cos 65° y-dir: 2000 kg * 0 m/s + 1500 kg * 15 m/s = 3500 kg * vABy * sin 65° vABy = (1500 kg * 15 m/s) / (3500 kg * sin 65°) = 7.1 m/s With the value for vABy, I try to find the find the value for the second side and the hypotenuse with trigonometry: vABx = vABy / sin ∅ = 7.1 m/s / sin 65° = 7.83 m/s. With the Pythagorean theorem, I can now find the hypotenuse, and the velocity that the two enmeshed cars have: vAB = √(7.12 + 7.832) = 10.6 m/s. Looking at the solution, this is clearly not the correct answer. Can anyone see where my mistake is?