Explain the following statement: a concentrated acid is not necessarily a strong acid.

Can someone explain to me how to do this problem ?

In a game of pool, ball a is moving with a velocity v0 of magnitude v0 = 15 ft/s when it strikes balls b and c, which are at rest and aligned as shown. knowing that after the collision the three balls move in the directions indicated and assuming frictionless surfaces and perfectly elastic impact (that is, conservation of energy), determine the magnitudes of the velocities va, vb, and vc.

Which is a substance that can be separated by physical means and is not the same throughout