A smooth steel ball P (mass m) slides on a frictionless horizontal table with a speed of 6 m s⁻¹ towards an identical stationary ball Q. The collision is perfectly elastic. After impact, ball P is observed to move at 30° above its original line of motion. What is the speed of ball P immediately after the collision?
a) 6m s−1
b) 3m s−1
c) 5.2m s−1
d) 6.9m s−1