physics
posted by Anonymous .
An unstable nucleus of mass 17x10^27 kg, initially at rest, disintegrates into 3 particles. One of the particles, of mass 5x10^27kg, moves along the positive y axis with a speed of 6.0x10^6m/s. Another particle, of mass 8.4x10^27kg, moves along the positive x axis with a speed of 4x10^6m/s. Determine the third particle's speed and direction of motion. For now you may assume that mass is also conserved in the disintegration process.
I started by multiplying the mass with the velocity. Then, I don't know.

Remember that momentum is a VECTOR. The direction and magnitude are both important. You must resolve the MV product into x and y components to solve this problem.
Apply conservation of momentum in a plane with x and y axes. All motion is in that plane. You will end up with two equations in the two unknown components of velocity of the third particle, Vx and Vy. From those two components, compute the magnitude (speed) and the direction of motion (arctangent Vy/Vx).