In case of brake failure, why isn’t going resverse and gassing correct solution?
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When it comes to friction, there are two separate cases between every pair of objects: static friction, where the two objects are stationary relative to each other, and sliding friction, where the two objects are sliding past one another.
The sliding friction is almost always weaker than the static friction.
Find a slightly heavy object and put it on a tabletop. Then, use your hand to apply a small pressure on it, small enough so it doesn’t move. That pushback you feel is the static friction between the object and the table. Increase the pressure on the object until it begins to slide. The moment it begins sliding, you should feel a bit of a “give”, where the item now presses back against your hand with less force than it did when it was sitting still. Now you’re feeling the sliding friction, which is lesser than the static friction. If you let up on the object enough such that the sliding friction wins out, it will come to a stop. It will almost feel like it “sticks” a little bit, because the force you were just using to push it along isn’t enough anymore. You’d need to overcome the static friction to get it moving again.
When braking in a car, it’s always best to always let your tires roll along the road in such a way that they do not slip. That way, you get the full force advantage of static friction to slow you down. If your tires start to slip at all, you lose static friction and now only get the sliding friction, which is weaker, and won’t slow you down as quickly. And as a negative bonus, you also lose all of your steering, because that relies on friction too. So you want to avoid sliding if ever possible.
If you ever do start sliding, it’s actually best to *stop* braking, allow your tires to match the speed of the road again to get the static friction buff back, and re-brake. This is the “pump your brakes” adage that drivers of older cars had to learn. Modern cars have a system called the Automatic Braking System (ABS) that will do this for you very rapidly. You may hear it as a grinding noise and feel it as a bumpy sensation when it engages. If you drive a car made in the last several decades, do *not* pump your breaks, just floor that brake pedal with everything you’ve got. The ABS can pump the brakes way better than you can.
If your brakes give out, reversing is a terrible alternative. Not only will it wreck your transmission if you and your car survive, but it will certainly make your tires start sliding. And curious thing about sliding friction, it doesn’t matter how fast the tires spin, the friction doesn’t get any better. Once you’re sliding, you’re stuck with that worse friction no matter how hard you reverse. And now you’ve lost any steering control you had on top of that, too. Not good. A better option is to simply gear down. It’s not as good as braking, but it hopefully won’t put you into a slide.
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