In case of brake failure, why isn’t going resverse and gassing correct solution?
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Down shifting is a natural way of slowing your car down. Yes you can down shift in an automatic
That’s a quick way to grenade your transmission. Better solution would be to down shift and find a runaway ramp/something safe to stop you.
Putting your car into reverse while moving forward wont do anything. Basically when you put your car into reverse a gear slides into place which then lets it happen. While moving forward this gear would be trying to slide into place with another gear thats rapidly going the wrong way. You might hear some grinding but its not possible for this gear to get into place while moving forward. So nothing at all will happen. The only time you can change to reverse is when the car is stopped.
A few people have already answered about why reverse wont work and to downshift so i’ll just add that cars have a handbrake/emergency brake. Very gently lifting this will start to engage the brakes using the brake cable rather than the hydraulic footbrake system. Some cars dont allow the handbrake to work while moving though to prevent the wheels locking up, including mine (which makes handbrake turns impossible, annoyingly) but my old car could do this
From first hand experience I can tell you that you’ll probably break something.
Years and years ago I had an old beater POS car. It was an automatic and the gate to move between gears was broken. Without pushing the button on the shifter I could just slap it into any position. One day I was driving on a highway with my two brothers in the car, we were doing about 45mph. They were horseplaying and screwing around with each other between the front and back seat. One of them accidentally kicked the shifter and it went straight into reverse. The car made a loud sound and I quickly put it back into drive and kept going. The next time I tried to use reverse the car would reverse but extremely slowly – basically a slow crawl. You could rev the gas and it wouldn’t make it move much faster. We used to joke that the reverse gear only had two teeth left.
If you could theoretically put you car into reverse while moving foward , spinning the wheels in reverse would technically slow the car but not nearly as fast as the wheels do not have grip with the road (look up Anti lock breaking system or ABS to understand this stuff more) it also would make your car loose control as you wheels no longer have grip as they are sliding on the ground
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.
This would be analogous to you sprinting at full speed forwards, then immediately running backwards. Not slowing down, just running backwards immediately.
You couldn’t physically do it because you just can’t reverse that quickly.
You could also compare a bit to putting a treadmill on full speed then just jumpinh on and sprinting from the start. This is a bit easier to be fair as you’re not quite going backwards, but it’s the same idea of accelerating very quickly.
When you put the car in reverse it will immediately try to spin the wheels backwards. If they’re actually moving forwards at the time that puts an immense strain on the transmission system and would probably grind it to bits.
You could gradually go down in gears, which would gradually slow it down. This would probably still do some damage but significantly less and you stand a chance of not destroying the transmission system.
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