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1. when passing an oncoming truck on the highway, your car tends to sway toward the truck?
2. the canvas roof of a convertible automobile bulges upward when the car is traveling at high speeds.
3. the windows of older trains sometimes break when a high-speed train passes by on the next track.

2007-03-12 14:05:48 · 9 answers · asked by questionhere 2 in Science & Mathematics Physics

please explain in simple physics terms, its okay if you only answer one of them, thnx

2007-03-12 14:06:24 · update #1

9 answers

Sounds like Bernoulli's Principle for fluids. Moving fluids create a lower pressure so that there is a pressure difference that can push objects from the high to the low pressure area.

2007-03-12 14:12:08 · answer #1 · answered by hello 6 · 1 0

Bernoulli's Principle, which states that when a fluid moves, pressure drops.
This is how it applies to your 3 scenarios:

1. When you pass an oncoming truck, there is a layer of high-velocity wind behind it, which is now on the side of your car. On the other side of your car, there is regular atmospheric pressure air, which exerts more pressure on your car, causing it to sway towards the truck.

2. As high-velocity wind passes on top of your canvas, the higher-pressure air below the canvas exerts more pressure upward than the air on top of it does downward, so the air below it pushes the canvas up.

3. When a high-speed train passes by, there s high-velocity wind on the side of the older train. The windows may be of poor quality, and easy to break. The higher pressure inside the old train pushes against the window, and the lower pressure air outside causes the pressure inside to push enough that the window may break.


Cheers!

2007-03-12 14:23:06 · answer #2 · answered by pedros2008 3 · 0 0

All are Bernouille's Principle

1...A truck, being bigger than a car causes a greater partial vacuum due to its velocity than the car.
The pressure difference between your car and the truck tends to push you towards the truck.

2...The canvas roof, at high speed, is causing a lower pressure above the car due to its curvature. The car's internal pressure causes the roof to bulge.

3....Older trains were not as sturdily built as modern ones..
Again, the passing of the high-speed train causes a partial vacuum and, the air pressure in the older train, acting against the large surface area of the window has sufficient pressure difference to blow a window out. (If the window was partly open it probably wouldn't happen).

2007-03-12 14:39:28 · answer #3 · answered by Norrie 7 · 0 0

Bernoulli's Principle states that the faster a fluid flows, the lower the pressure it imparts.

In case 1. As the truck passes your car it causes the air (fluid) between the truck and the car to move. Think of it as the truck pulling the air with it. On the other side of your car the air is not moving (well, you can think of it that way). So the air is moving faster resulting in a LOWER pressure. The difference in pressure "pushes" your car toward the truck.

In case 2. The air outside the car is moving (lower pressure) while the air inside the car is not (at least relative to the roof). Again ... higher pressure in the car relative to outside the car.

In case 3. Air outside the train is moving while inside is not relative to the window ... higher pressure inside vs outside. Window blows out.

By the way. This is the same principle that keeps planes flying. The shape of a plane's wing makes the air above the wing move faster than the air below the wing. So ... faster air above ... lower pressure ... slower air below ... higher pressure. High pressure pushes up and plane flies !

2007-03-12 14:24:13 · answer #4 · answered by M Y 1 · 0 0

The Bernoulli equation. When a gas at a given pressure and velocity is accellerated to a new velocity, it exerts less pressure in the direction orthagonal to the movement.

This is also why a wing provides lift.

2007-03-12 14:09:40 · answer #5 · answered by Anonymous · 0 0

physics principle underlies observations

2016-02-01 05:41:04 · answer #6 · answered by Janean 4 · 0 0

It could be either the Bernoulli Principle or differential pressure.

2007-03-12 14:23:48 · answer #7 · answered by Anonymous · 0 0

Bernoullis Principle.

HTH ☺

Doug

2007-03-12 14:11:32 · answer #8 · answered by doug_donaghue 7 · 0 0

I often end up asking the same question on other sites

2016-08-23 21:01:09 · answer #9 · answered by Anonymous · 0 0

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