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#141616 - 12/17/10 03:13 PM Re: Bowling - Spinner/Helicopter/UFO Style ***** [Re: aoiten]
Mkirchie Offline
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Registered: 01/14/07
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Both of your examples do not work, a car that is slowing down without locking its brakes is not rolling and a car that is speeding up without spinning its tires is not rolling. So, rolling friction does not apply. A pure roll is when the forwards translational velocity of a point on the wheel due to the car's forwards motion matches the backwards translational velocity of the point on the wheel due to its rotation without any other forces maintaining this state. This is not the case in either of your examples. I can explain later, but I have to leave work. Here is a link for now that explains the difference between static friction, sliding friction, and rolling friction.

http://hyperphysics.phy-astr.gsu.edu/hbase/frict2.html
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#141623 - 12/17/10 04:36 PM Re: Bowling - Spinner/Helicopter/UFO Style [Re: Mkirchie]
Mkirchie Offline
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Ok, here is the explanation related to your example. You are driving a car at 50 mph on a level road and you put the car in neutral. Ignoring air resistance, rolling friction will eventually make the car stop, but it would take a very long time because rolling friction is very weak due to the fact that the coefficient of rolling friction is very small.

If you were to press on the brakes to stop, but not slam on them, the point on the tire will slow down gradually relative to the forward motion of the tire. This will make the tire want to start sliding, but static friction between the tire and the road will keep it from sliding and provide the force that will slow the car down. This will be the case as long as the tire slows down with a small enough acceleration to keep the force needed to slow down the forwards motion of the tire smaller than the force of static friction. Since the coefficient of static friction is the greatest of these three types of friction, the car will stop the quickest of the 3 examples.

If you slam on the brakes to stop, the backwards motion of the point that touches the road will slow down and stop suddenly relative to the forwards motion of the tire. The force needed to slow down the tire's forwards motion and to keep the tire from sliding will be very large and greater than the force that static friction provides, so the tires will then start to slide and sliding friction will take over. Since sliding friction is weaker than static friction but stronger than rolling friction, this case will be the case where the time it takes to stop falls in-between the times for static friction and rolling friction.

Almost the same thing works when the car is speeding up. Press on the gas pedal gradually and the static friction will make the tires start to move forward without them spinning because you have not passed the limit of static friction. Press on the gas pedal suddenly and the static friction will not be great enough to make the tires move forwards, so the tire will start to spin. Rolling friction cannot make a car move forwards if it is at rest, it only stops the motion of a rolling object.

The same reason explains why you can't control a turn when the wheels are locked. Locked wheels cause sliding friction which is weaker than the static friction that occurs when the car starts to change direction. And, when you try to change direction too fast by turning too hard, the car needs more force to keep it turning than static friction can provide.

Mark
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#141624 - 12/17/10 04:36 PM Re: Bowling - Spinner/Helicopter/UFO Style [Re: KahKiat]
Time-To-Roll Offline
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This is one of the most educational posts I have read for awhile. I have always thought the spinner is a good method for women bowlers, but there has never been enough information as to the ways to achieve it. I have some good ideas now, thanks to all the videos and imput on this post.

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#141629 - 12/17/10 05:31 PM Re: Bowling - Spinner/Helicopter/UFO Style [Re: Time-To-Roll]
aoiten Offline
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Registered: 03/03/10
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Originally Posted By: Time-To-Roll
This is one of the most educational posts I have read for awhile. I have always thought the spinner is a good method for women bowlers, but there has never been enough information as to the ways to achieve it. I have some good ideas now, thanks to all the videos and imput on this post.


Wow, very happy to hear that you're interested in spinning. If you want more information just let me know. I think spinning can definitely be an effective and competitive technique for women, especially smaller women.

The physics of the technique is still up for debate. haha But who cares as long as it works for you.

I did a little spinning yesterday after working on two-handing for the past two weeks. Opened with three strikes, then 9-spare. Then I started playing with some different concepts so my game started going down hill from there. Still, I felt the ease and effectiveness of the shot.

(What I didn't like is the same thing I don't like about conventional techniques: Thumb issues.)

Anyway, good luck and have fun.

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#141636 - 12/17/10 06:41 PM Re: Bowling - Spinner/Helicopter/UFO Style [Re: Mkirchie]
aoiten Offline
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Registered: 03/03/10
Posts: 1415
A/S/L: amerika ni sunde iru


Reading and responding to the first post first. Here's a quote from the linked page:

"A rolling wheel requires a certain amount of friction so that the point of contact of the wheel with the surface will not slip. The amount of traction which can be obtained for an auto tire is determined by the coefficient of static friction between the tire and the road. If the wheel is locked and sliding, the force of friction is determined by the coefficient of kinetic friction and is usually significantly less."

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#141639 - 12/17/10 06:50 PM Re: Bowling - Spinner/Helicopter/UFO Style [Re: Mkirchie]
aoiten Offline
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Registered: 03/03/10
Posts: 1415
A/S/L: amerika ni sunde iru
Responding to the second post: Ah! The problem is that I was using the wrong term. When I referred to the rolling ball, I was referring to static friction, not rolling friction.

BTW, the link was good reading with a nice plot of what I was seeing in my head.

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#141640 - 12/17/10 07:14 PM Re: Bowling - Spinner/Helicopter/UFO Style [Re: Mkirchie]
ebon betta Offline
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Registered: 11/11/10
Posts: 488
A/S/L: 54/m/nyc /ny2
Boy looks like a lot of miss informed technical babble going on here.
You hit the brake and the wheels gets increased resistance to spin PERIOD. Which in turn creats some friction to the ground but the major impetues is to the spinning of the wheel. on a flat surface take your foot off the gas you have drag from the car, axels and some resistance from the ground since the wheels are rubber and deform as it spins. Use hard wheels and the major friction is every little bit of dirt that gets under the wheel contact area. Also realize that with tires we are talking about a much larger contact area than a bowling ball.
also when turning a lot of the friction that slows a car comes from the combined caster and cambers the wheels are set at, as well as the fast that the rubber tire wants to twist and go straight.

But much of this has little to compare to a bowling ball.

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#141645 - 12/17/10 10:46 PM Re: Bowling - Spinner/Helicopter/UFO Style [Re: ebon betta]
Mkirchie Offline
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Registered: 01/14/07
Posts: 852
A/S/L: 38/M/New Jersey
Quote:
But much of this has little to compare to a bowling ball.


That is one of the points that I forgot to make earlier about there being a very large difference between a bowling ball and a car tire. I was trying to illustrate the difference between rolling friction and sliding friction using the example given, which is not an exact match. The amount of rolling friction on a bowling ball would be much smaller due to the fact that the deformation of the ball tiny in comparison to that of a car tire.

I do respectfully disagree about your view of friction between the tire and the road and its relationship to braking, you are greatly minimizing its significance. Basically, if friction does not play a major role when the wheels slow down, the car will stop even if it is moving on a completely frictionless surface and how you press on the brakes is not at all determined by road conditions like wet or icy, it would work out to be the same. For a car (or any mass) to change its velocity, there must be a unbalanced force exerted on the object by another object, this is Newton's 2nd Law of Motion. If the tires slow down and friction from the road surface does not provide this unbalanced force to stop the car, there are no other objects outside of the car to provide the unbalanced force on the car to stop it from moving.

Mark
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#141659 - 12/18/10 12:46 AM Re: Bowling - Spinner/Helicopter/UFO Style [Re: KahKiat]
aoiten Offline
Legend

Registered: 03/03/10
Posts: 1415
A/S/L: amerika ni sunde iru
What I am talking about is not rolling friction. I see a bowling ball as having static friction when rolling and kinetic friction when sliding. A rolling ball should have more drive and less deflection, partly due to that static friction.

The coverstock of a ball is often compared to the tire on a wheel. If the coverstock is smooth and hard (plastic), it would slide like a tire on ice. If the coverstock is rough and soft (reactive), it might slip at first, but later it will grab, turn, then roll. That is how the hook technique works. Slide, hook, roll. The ball should not be slipping upon impact.

These are very relevant concepts. Just reverse them for the spinner. The spinner slips until impact and has less drive and more deflection. The slip is mainly due to the high torque of the tight spin of the ball. That puts the ball into kinetic friction mode, which allows it to slide down the lane easier.

OK, nevermind. Let's just stick with our own views of how things work. haha

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#141682 - 12/18/10 08:42 AM Re: Bowling - Spinner/Helicopter/UFO Style [Re: aoiten]
Mkirchie Offline
Hall of Famer Contender

Registered: 01/14/07
Posts: 852
A/S/L: 38/M/New Jersey
Exactly, that's where you were caught up was the difference between rolling with static friction, rolling with rolling friction, and sliding with kinetic friction.

Just one thing about torque, it's a stranger concept than most people realize, ideas in rotational motion are very strange compared to ideas in linear motion. Torque is the product of force and distance from the axis of rotation of an object. It is the rotational version of force, in linear motion, forces change the linear momentum of an object due to its linear motion, in rotational motion, torque changes the angular momentum of an object, which is due to rotation. When you roll a ball down lane and it gets to the dry boards, the force of friction times the distance from where the ball touches the lane to the axis of rotation determines the torque which then determines how quickly the ball will gain angular momentum, thus increasing the rotation of the ball until it reaches the state of rolling you mentioned in the post. As this is happening, the linear velocity of the ball is also getting smaller due to friction, which also helps to get the ball out of the slide and into the roll phase. Since the axis of rotation is very close to parallel to the lane surface for a semi-roller, the axis is far away from where the ball touches the lane for a semi-roller and the torque will be large, bringing the ball to a roll sooner. When you release a spinner, the axis of rotation is much closer to the point where the ball contacts the lane, so the torque will be much smaller and will bring the ball to a roll much later, so the ball will be sliding all the way down lane and slide when hitting the pins. As you know, this is an important aspect of the spinner bowler's technique.

I think I answered what might have been the original point about effects of friction on the two shots. The friction force will be the same for both styles if we ignore the other effects like the ball rolling over the already oil covered track. How that friction brings affects rotation and thus how quickly it goes from sliding to rolling all depends on torque, which depends on how far this axis of rotation is from the point where friction is acting on the ball.

Mark



Edited by Mkirchie (12/18/10 09:14 AM)
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