then load the truck with heavy stuff, so much that the tire is bulging with the load, why is there still only 80 pounds of air in the tire?
2006-08-26 19:00:19 · 10 answers · asked by rera1397 3 in Science & Mathematics ➔ Mathematics
I mean, why doesn't the PSI increase?
2006-08-26 19:08:38 · update #1
NOBODY GOT IT!
The trick here is that the tire is bulging, another way of saying it covers a bigger patch of pavement. Same pressure (or maybe ever so slightly more), but the contact area on the ground increases in proportion with the load applied. F = p*a
More area with a constant p gives more force.......
2006-08-26 19:20:36 · answer #1 · answered by Steve 7 · 2⤊ 1⤋
What holds up the truck is total force. If a truck weights 8000 pound-force, the tires must push back 8000 pound force. If the tires are filed with 80 psi of air, the road contact area must be 100 square inches (80 psi x 100 si = 8000 pounds force). So as you place more weight on the truck, the tires bulge and the area increases.
That is theory, but in practice, the pressure does go up because modern tires at heavily reinforced with steel and fiber glass cables. They are not balloons. They are designed to hold a certain shape. The area it contacts with the road does not increase the same amount as the load. So in practice, the pressure does go up somewhat. If you put a pressure gauge on a basketball and you jump on it, you would see the pressure change. If an elephant stepped on the basket ball, it should never burst because the area should increase. But in reality, the pressure does go up until it bursts when the internal pressure exceeds the limit of the strength of the basketball.
2006-08-26 19:38:59 · answer #2 · answered by Kitiany 5 · 1⤊ 0⤋
kitiany's got the right answer
your original premise was false, the pressure does not stay at 80, the pressure increases and there is also some increase in the surface area, as steve talks about
a good reality check for the surface area response that steve gave is this: if you have a single car tire that is not on a car but is in the same position that it will be when it is on a car is touching the ground and there is only the weight of the tire pressing down-maybe 30 pounds. when that same tire is on a car, it might be supporting one fourth of the cars weight-lets say 900 pounds. the surface area of the tire making contact with the ground has not increased by a factor of 30.
of course the amount of air in each tire is constant, but psi is not a measurement of how much air is in a tire, it is a measurement of how much pressure is pressing on each unit area of the tire (on average, of course)
so the answer to your question is....there is not only 80 psi, the pressure will have increased, but by less than the ratio of the added weight.
2006-08-26 19:49:38 · answer #3 · answered by Anonymous · 2⤊ 0⤋
the air in the tire is the air in the tire, no matter what you load in the truck bed the air in the tire is the air in the tire,
2006-08-26 19:13:35 · answer #4 · answered by ? 5 · 0⤊ 0⤋
If the cross sectional area of the tyre is reduced by the load then the pressure will increase.
2006-08-27 10:37:31 · answer #5 · answered by John A 3 · 0⤊ 0⤋
It will ride like **** . and the tire only needs 32 psi in it.
2006-08-26 19:09:20 · answer #6 · answered by canivieu 5 · 0⤊ 1⤋
Because the air has no place to go. (cksq)
2006-08-26 19:06:31 · answer #7 · answered by CKRT SQRL 5 · 1⤊ 1⤋
is it because air is a gas that can be compressed it takes up less space whilst maintaining same pressure. Molecules compress . That is why we have hydraulic fluid..............
2006-08-26 19:14:27 · answer #8 · answered by justin b 1 · 0⤊ 2⤋
because air cannot get out of tire
simple!
people are making it complex
LOL!!!!!!!!!!!!
2006-08-26 22:59:28 · answer #9 · answered by Navdeep B 3 · 0⤊ 0⤋
because the tire is closed... not a single air will get out of it... duh... did you ever saw a tire that is open?
2006-08-26 19:36:58 · answer #10 · answered by Sara P 1 · 0⤊ 1⤋