How do spikes reduce slipping in running?

[aspodkfpo]

Homework Statement

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Relevant Equations

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Does wearing spikes increase friction if so how?

Is the main benefit of wearing spikes because it allows the runner to push against the side of the hole it makes, therefore directing a portion of the normal force forwards, unlike normal running where friction pushes the runner forward?

Middle and long distance runners in track often don't wear shoes with spikes. This is because they aren't pushing hard enough that there is a risk of slipping https://kaitcphysicsoftrack.weebly....rip onto the,spike makes - no friction needed.

How does not pushing hard enough result in a risk of slipping? Or is this statement untrue and if so why?

 

[PeroK]

Because of the coefficient of friction, there is a maximum horizontal force through contact with the ground. This also depends on how hard you can push into the ground.

If you want more than the maximum you get from simple friction then you need spikes. Sprinters may need this at least for the high acceleration phase.

Ultimately, using spikes on a good track may be less efficient, which is not a problem for sprinting but is for longer distances.

 

[aspodkfpo]

Because of the coefficient of friction, there is a maximum horizontal force through contact with the ground. This also depends on how hard you can push into the ground.

If you want more than the maximum you get from simple friction then you need spikes. Sprinters may need this at least for the high acceleration phase.

Ultimately, using spikes on a good track may be less efficient, which is not a problem for sprinting but is for longer distances.

Why is it less efficient? It seems like getting spikes into the ground doesn't take anymore energy than running without spikes?

 

[PeroK]

Why is it less efficient? It seems like getting spikes into the ground doesn't take anymore energy than running without spikes?

You might have to look at specific sports science to get the best answer to that. Spikes have to be pulled out of the track with every step. Over a distance race that small extra effort might make a small difference. If you take the extreme case of very long spikes, then clearly it would be an effort to move at all!

 

[aspodkfpo]

You might have to look at specific sports science to get the best answer to that. Spikes have to be pulled out of the track with every step. Over a distance race that small extra effort might make a small difference. If you take the extreme case of very long spikes, then clearly it would be an effort to move at all!

When being pulled out, friction is exerted by the side of the walls downwards, thereby resulting in more energy expended?

 

[PeroK]

When being pulled out, friction is exerted by the side of the walls downwards, thereby resulting in more energy?

Yes, there is friction on the sides when you pull something out. If you stick a knife or spike into something it takes effort to extract it. For running spikes that must be a small extra effort, but may add up over thousands of strides. And, if you don't need the extra grip that the spikes give you, then it's wasted effort. If you are sprinting, then the extra effort over a few dozen or a hundred strides is negligible, but the extra grip may be invaluable in powering along.

That's the simplistic theory I can give you. Note that I've qualified everything I've said, as I'm no expert in the science of running shoes. If you want to know more, then I'm sure the Internet has plenty on the sports science of running spikes.

 

[jbriggs444]

When being pulled out, friction is exerted by the side of the walls downwards, thereby resulting in more energy expended?

Then you push them in, you are dissipating energy into kinetic friction. When you pull them out, you are dissipating energy into kinetic friction. It is a lose-lose situation.

 

[haruspex]

Then you push them in, you are dissipating energy into kinetic friction. When you pull them out, you are dissipating energy into kinetic friction. It is a lose-lose situation.

Yes, wrt the pushing in, in effect you are running uphill slightly, like running on soft ground.