### Question

Does a car makes more pressure to the floor when it goes faster, or the car could fly if it goes even faster?
Asked by: Miguel Angel Monroy Meneses

What an interesting question. This kind of question shows that you are thinking because on the one hand it seems to make sense that the faster a car goes the harder it must push on the floor to go fast. but on the other hand it doesn't quite sound right. So, this kind of question shows that you are thinking about what you are thinking and that is always a good thing to do.

OK, now to answer your question. The pressure the car applies to the floor is a function of the weight of the car and area of the car's tires. The equation P=F/A is the equation. This pressure cannot change unless either the weight or the area of the tires changes. Do you think that by going faster that either of these two things can change? Under normal conditions, the answer is 'no'. Whatever the car weighs it weighs the same no matter how fast it goes. Whatever the area of the tires that are on the ground will also stay the same no matter how fast the car goes. But, all of this is only under normal conditions.

Some cars have spoilers on the back end. Do you know that these are supposed to do? Well, if a car goes fast enough and if the spoiler is designed correctly the car will have the opposite of what an airplane has to make it fly. Call it anti-lift. The shape of the spoiler causes the car to have more weight sue to the flow of air over the spoiler. So, the faster the car goes the less chance it has of flying. Do you think you could turn the spoiler upside down and get lift like an airplane? You could do this but the lift would not be nearly enough to raise the car off the ground.

Now, you may have seen movies where cars that go very fast seem to fly off the ground. This is precisely because they are going so fast. As Newton's first law states: An object in motion will stay in motion in a straight line at a constant velocity unless an unbalanced force acts upon it. Cars that go very fast and also go up a short incline will keep going up after they have passed the end of the incline and since the velocity is so high they will travel a long distance before coming back to the ground. They are not flying because of their great speed so much as because of their great inertia combined with speed over a ground that falls away giving the illusion of having flown.
Answered by: Tom Young, M.S., Science Teacher, Whitehouse High School, Texas

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### Science Quote

'There must be no barriers for freedom of inquiry. There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors.'

J. Robert Oppenheimer
(1904-1966)