Pelican Parts Forums

Quote:

Originally Posted by RWebb (Post 3765004)

OK, let's see how you do -- if you know the source please don't post it for a few days.

1. If you hold your hand out the window while riding in a car (carefully!), you feel more drag if you hold your hand perpendicular to the ground compared to parallel to the ground. Why?

2. In Nascar’s “old car” — the one used before the Car of Tomorrow being introduced this season at Daytona — the fenders on the left-hand side of the car were much broader than on the right-hand side of the car. If the air on both sides of the car had the same pressure, what would the advantage be of having broader fenders?

3. When you place a tire pressure gauge on your tire and measure a number like 30 psi, that’s not the actual air pressure in your tire. What is the actual air pressure in your tire?

4. The temperature of the water in your radiator can actually get above 212 degrees Fahrenheit. Normally, water boils at 212 degrees, so how can this happen?

5. How much does the air inside the Unisphere weigh? The Unisphere is a model of the Earth made of a grid of stainless steel tubes, open to the air, with continents in solid stainless; diameter of the sphere itself is 120 feet, or 36.57 meters.

1. Since the air pressure due to the forward movement is constant, the greater the surface area presented to the airflow the greater the resisting force (drag).

2. The idea behind this would be to increase the drag acting on the left hand side of the car which would give the car a natural tendency to turn to the left.

3. What you are measuring is the relative pressure of the air in the tire, that is the pressure relative to atmospheric pressure. The pressure you are measuring inside the tire need to have the atmospheric pressure added to it to give you the absolute pressure.

4. The cooling system on most modern vehicles is pressurised above atmospheric pressure. The boiling point of a liquid is directly proportional to pressure; increasing with increased pressure and decreasing with decreased pressure. Hence the increased pressure in the cooling system increases the boiling point of the water.

5. I have to assume that the air 'inside' the Unisphere could be captured at any one instance and measured. I also have to assume that the dimensions given are the inside diameter of the sphere as no dimension is given for the thickness of the material. Additionally I am assuming that the Unisphere is at sea level at a temperature of 20 degrees Centigrade so air density is 1.2kg/m^3.
Given these assumptions as fact then the volume enclosed by the sphere is 25,607m^3 so the weight of the air would be 30,728 kg.

Good luck getting air on a scale!