Two frictionless discs on an air table, initially at rest, are driven apart by an explosion with velocities of 9.0m/s and 5.0m/s. What is the ratio of their masses?

Question

beth12345 · Answer

the answer I am given is    0.56      but I don't know how to get it

anonymous · Answer

Well, the momentum of the discs will be equal to each other after the explosion, so with
p1=m1v1 and p2=m2v2 and p1=p2, if you plug in the velocities you get p1=9m1 and p2=5m2. Then, you set p1 equal to p2, so 9m1=5m2 and isolating for the ration of m1/m2 you get m1/m2=5/9, or 0.56

beth12345 · Answer

ooh, ok thank you :)