Posted by bob on .
A billiard ball traveling at 8.0 m/s has an elastic collision with a second billiard ball of equal mass that is at rest. After
the collision, the first ball is at rest. What is the velocity of the second ball after the collision?

physics 
dida,
v1=8m/s, v2=0 , m1=m2>m , v=?
m1*v1+m2*v2=(m1+m2)*v
m*8+m*0=(m+m)*v
8m=2m*v
8m/2m=v
4=v
v=4m/s