A 5-degree angle will cross 5 boards over 5 feet. The angle is the number of boards the ball is crossing over a 5-foot distance. A typical launch angle is 1 to 3 degrees. A typical entry angle is 3 to 7 degrees. The ball is constantly loosing speed due to friction between the ball and lane.
Friction is the major factor in determining how much a ball hooks.
Without friction a ball would never hook. Lane oil reduces the friction and allows the ball to retain its initial velocity longer. The friction in the oiled area of the lane is very small measuring about .01 to .06. This causes the ball to loose about 1 mile per hour in velocity in the first 40 feet of the lane. The friction on the dry backend of the lane is about 5 to 25 times greater which is why the ball hooks so much more on the backends.