Questions from Modern Physics

Q: In a store-window vacuum cleaner display, a table-

In a store-window vacuum cleaner display, a table-tennis ball is suspended in midair in a jet of air blown from the outlet hose of a tank-type vacuum cleaner. The ball bounces around a little but alwa...

Q: A tornado consists of a rapidly whirling air vortex. Why is

A tornado consists of a rapidly whirling air vortex. Why is the pressure always much lower in the center than at the outside? How does this condition account for the destructive power of a tornado?

Q: Airports at high elevations have longer runways for takeoffs and landings than

Airports at high elevations have longer runways for takeoffs and landings than do airports at sea level. One reason is that aircraft engines develop less power in the thin air well above sea level. Wh...

Q: When a smooth-flowing stream of water comes out of a

When a smooth-flowing stream of water comes out of a faucet, it narrows as it falls. Explain.

Q: Comparing Example 12.1 (Section 12.1) and

Comparing Example 12.1 (Section 12.1) and Example 12.2 (Section 12.2), it seems that 700 N of air is exerting a downward force of 2.0 × 106 N on the floor. How is this possible?

Q: Equation (12.7) shows that an area ratio of

Equation (12.7) shows that an area ratio of 100 to 1 can give 100 times more output force than input force. Doesn’t this violate conservation of energy? Explain.

Q: You have probably noticed that the lower the tire pressure, the

You have probably noticed that the lower the tire pressure, the larger the contact area between the tire and the road. Why?

Q: In describing the size of a large ship, one uses such

In describing the size of a large ship, one uses such expressions as “it displaces 20,000 tons.” What does this mean? Can the weight of the ship be obtained from this information?

Q: A rigid, lighter-than-air dirigible filled with helium

A rigid, lighter-than-air dirigible filled with helium cannot continue to rise indefinitely. Why? What determines the maximum height it can attain?

Q: A rubber hose is attached to a funnel, and the free

A rubber hose is attached to a funnel, and the free end is bent around to point upward. When water is poured into the funnel, it rises in the hose to the same level as in the funnel, even though the f...