Why do cars not accelerate uphill?

Answer 1

It takes power to move a car. If the car is on level ground, a moving car takes power to overcome the drag of the air it moves through, as well as to overcome the friction of the tires against the pavement. All cars have more than enough horsepower to overcome these losses, and the excess horsepower can be used to accelerate. Of course cars use a little horse power to charge the battery, run the air conditioning, power the lights and stereo, etc. It all adds up! A car travelling uphill has to overcome one more loss, that is, the power required to physically lift the weight of the car as it moves uphill. Imagine if you had to lift your car straight up a thousand feet. It would take a lot of effort, right? Well a car that drives to the top of a 1,000 foot hill needs the same amount of power to raise the car that high. The faster it goes, the more power needed to do the work of lifting all that weight. There is only so much horsepower available in each car. So if the car is moving uphill, and the horsepower needed to overcome air drag, plus tire friction, plus power to lift the car equals the horsepower available, there is no more power left to accelerate! That having been said, you should know that some cars with very powerful engines DO have enough horsepower to accelerate while going uphill. And even small-engined cars can, under certain circumstances. Take your average low-horsepower car, put it in the lowest gear, and get moving uphill at, say 5 miles per hour. Stomp the gas down, and just about any car will go faster, say 15 MPH. See, you have accelerated! The reason is since you are not going fast the friction and drag is lower giving you some excess horsepower. At the lower speed, you are also taking more time to lift the weight, so less power is needed. What you really meant by your question, I think, is why a car travelling at normal highway speeds can't accelerate to an even faster speed while going uphill. That's where the friction and drag losses come in to play, and of course the faster you want to raise the weight of the car upward, the more power it takes.