Question

Ball 1, with a mass of 20kg, is moving to the right at 20m/s. At what velocity should Ball 2, with a mass of 40kg, move so that they both come to a standstill upon collision?

Answer 1

let the velocity of second ball be v.
so total initial momentum= 20*20 + 40*v
Finally, since both balls come to a standstill, final momentum=0
By conservation of momentum
Initial momentum=final momentum
20*20+40*v=0
therefore, v=-10 m/s

Answer 2

thank you