Work of 36 joules is done on ball a. it travels a certain distance and hits ball b. ball b, which was stationary, starts to move at 12 m/s. if this is an elastic collision, then what was the initial velocity of ball a? (both balls have a mass of 500 g. ignore changes due to friction.)

here collision between two balls is perfectly elastic collision

and the friction force is considered to be zero

now here we can say that momentum conservation is applicable here

here we know that two balls are of same mass then we can say

divide whole equation by mass "m"

now it is also given that it is elastic collision between two balls

now by solving the above two equations we have

so here given that

so the initial speed of ball A was same as final speed of ball B which is given as 12 m/s.

So here final answer will be 12 m/s