When a bowler bowls with a hook ball, they are taking advantage of friction. A hook ball is when the ball goes about two-thirds of the way down the lane before curving into the pins. Don't bowl against people who do this, they are usually very good. The lanes are oiled, producing a small coefficient of kinetic friction. Therefore, it takes a long time and a lot of torque on the ball to cause it to curve into the pins. The ball accelerates to the left or right as it catches what little friction it can.

The reason most good bowlers bowl with a hook ball boils down to the direction of the collision with the pins. Throwing the ball straight down the lane, while easy to do, does not distribute the impact efficiently. Once in a while a straight-ball bowler will get lucky and put a large X on the score chart, but more often than not they will get a split instead. It's best for the ball to collide between the head pin and one of its neighboring pins at roughly a 30° angle to distribute the force of impact evenly throughout the arrangement of pins. Any time one group of pins flies around in violent motions while others stand still as if nailed to the ground, this tells the bowler that they did not distribute the force of impact efficiently.


source: http://ourworld.compuserve.com/homepages/kennmelvin/tHook.htm

f_k = μ_kn
f_k = force of kinetic energy
μ_k = coefficient of kinetic friction
n = normal force