Please help me with this, as I'm not even sure where to start. Two children are standing on a 150kg wagon which is at rest. The children jump off the wagon in opposite directions. The 40kg boy jumps off at 4m/s and the 50kg girl jumps off at 2 m/s. What is the speed and direction of the wagon? As well as this one An explosion blows a rock into three parts. Two pieces fly off at right angles to one another. A 1.0Kg piece moves at 12m/s and a 3kg piece moves at 8m/s. Determine the mass and direction of motion of the third piece if it has a speed of 30m/s.