The Science Of Friction... Breaking down the Normal Force

What is the Normal Force

If you apply force to a surface, provided you are not able to make the object (rock) move, it will push back with an equal force. Forces can be broken down into smaller components that make up the total force. In order to identify the Normal Force, you have to do this in a way that focuses on the angle of the force in relation to the surface. The Normal Force will always be perpendicular to the surface that you apply the force to. So you have to break the force down with regards to this particular force component.

The applied force breaks down into two components, one that is parallel to the surface and one perpendicular to the surface. The parallel component is the one that may cause you to slip and the perpendicular is ultimately the one that prevents you from slipping. You should make every effort to ensure that you apply pressure that feeds the perpendicular component and that contribute as little as possible in the parallel direction. In non theoretical terms, putting your hand on a table top it is less likely to slip when pressing down on the table than when you press along the surface of the table top.

Perpendicular and angles, this spells trigonometry

If it has been a while, remember to think straight angles, squares. It's only if you need actual values for the forces and angles that you need to bring in sin and cosine to do calculations. When we climb, we really don't care how many newtons this and that force is, we only care for the direction we optimally should apply the pressure and in what scenario should we expect to start slipping.

Uneven surfaces

What then, when the surface is not even. It may be curved, it may have any shape or form. How can you break down the Normal Force for a surface like that? You have to think of the entire surface like many small sections of flat surfaces, and for each of these break down the forces in play and find the direction of its Normal Force. The combined Normal Force for the surface will be the sum of the Normal Force for each section.

This again gives you good information about how to handle the surface. Of all the sections, which gives the best use of the Normal Force in terms of creating friction, and which gives lousy contribution to the friction? Bearing in mind the direction that you might slip and what direction you care most about not slipping. You should try to use all the surface fractions that contribute well and avoid using those that don't. This way you can manipulate the combined Normal Force and thus the friction.

Applying more than one force

Just as with an uneven surface, there are other complexities to consider. Gravity is not the only force in play, you generate a series of forces with your muscles and these are not always aligned. The result is that more often than not, there are forces pulling in different directions and friction countering them in equally many opposite directions. Will friction win, and thus you... or will any of the forces overcome its respective opposing friction force? The resulting analysis is the same, break down each one separately and find the answer, but... keep in mind that one force may break down into a force component that contributes to another of the forces you consider and thus be the very thing that tips the scale and makes you slip.

To sum it up...

Analysis and consideration of how, when and why you slip and fail may not be a 5 second break between attempts. It may require careful consideration and many sleepless nights. My point is though, that this time is well spent, what else are you going to with that brain capacity? I'm not suggesting that you stop pushing the boundaries of your physical strength, I'm only suggesting that you also use your mind for analysis, rather than just counting pull-ups.

May The Normal Force Be With You!