Bowling

Bowling Physics

The following sections provide a crude, hand-waving explanation for certain facets of bowling. To make it useful, I've omitted some of the low-level details. All equations are left as an exercise to the reader. Q.E.D.

Conservation of Momentum - The Simplified Story

At the simplest level, bowling physics is simple:

Force you throw the ball = Force ball hits the pins - XYZ

If you throw harder, you hit the pins harder. This ignores things like how important it is to hit your target or the angle of impact, but it is basically correct as far as it goes.

But, what is "XYZ" ?

XYZ is the loss of power that occurs as the ball moves down the lane. These losses occur (from highest to lowest) from:

Friction with the lane as the ball moves
Translation between direction motion and rotation motion
Friction with the lane when the ball initially hits the lane

Let's take these one at a time:

Friction with the lane as the ball moves

As the ball rolls on the lane, it loses a little power from the drag and slows down. If there's a lot of oil on the lane, the ball slides and doesn't lose as much power because there's less friction.

All other things being equal, the farther the ball travels on the lane, the *MORE* friction eats away at its power because the ball travels farther on the lane.

Translation between direction motion and rotation motion

There are two separate but related forms of motion on the ball: directional and rotational. Directional motion is all about the position of the ball (speed the ball is thrown doen the lane, angle the ball is thrown relative to the lane). Rotational motion is about the spin of the ball.

A bowling ball starts with both directional and rotational motion. As it moves down the lane, the rotational motion changes the directional motion. This is what causes the hook. One way to look at it is that the rotational motion is "spent" to change the ball's direction. The more rotational motion, the more the ball's direction will change.

One key point: rotational motion can't become directional change when the ball is moving too quickly in a different direction. If you throw the ball hard, it won't start to hook until it slows down a little (due to friction #1, above).

Friction with the lane when the ball initially hits the lane

The thud when the ball hits the lane eats some of its power, especially if the ball doesn't land cleanly. A smooth release retains more of the power of the ball.

What can you do with this information?

IF THE LANES ARE OILY:

The ball is going to skid. It's not going to hook as much as usual, but it's going to arrive at the headpin with a little more power. You can improve your strike percentage by throwing a straighter ball higher onto the headpin. To carry the 5 pin, you need to hit the headpin at a sharper angle, so move your feet toward the outside of the lane and move your spot toward the middle of the lane.

IF THE LANES ARE DRY:

The ball is going to flip over. If you give it free reign, it will hook more but arrive with less power at the headpin. There is no physics-based improvement here. I generally advocate throwing harder to reduce the hook a little --- this is just to make the shot more predictable.

IF YOUR BALL IS HITTING TOO HIGH (on top of the headpin):

The ball has too much leftward directional motion. You need to start it farther right and/or throw it harder so it skids.

IF YOUR BALL IS FINISHING TOO LATE (behind the headpin):

The ball has too little leftward directional motion. You need to start it farther left and/or throw it slower so it starts hooking sooner.

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