Speed of a jet:

Hold your palm at arms length and look with one eye and count how long does it take for the plane to pass behind your hand. You’ll find it about 5 seconds. Your palm is 4 to 5 inches across and you’ll be holding it 3 feet away from your eye. The jet is at 30,000 feet, its cruising altitude, you might have heard the pilot saying it after it had completed its ascent. Thus plane is 10,000 times as far as your hand. Plane had to travel 10,000 palm widths to appear to cross your hand. That’s 10000 x 4 = 40000 inches. Plane travelled 40,000 inches in 5 seconds. There are 3600 seconds in an hour, 12 inches in a foot, 5280 feet in a mile. So its speed must be 40,000 / 12x5280x3600 = 454 mph.

Something similar to computing the distance of the cloud during a thunderstorm, you start timing the seconds from a lightening strike to hear the thunder sound, say it’s 10 seconds. Sound travels @ 300+ meters / second. Then the cloud must be 300 x 10 = 3000 meters i.e. 3 Kilometers away from you.

Weight of electrons to service US electricity needs:

Electric current is flow of atomic particles called electrons – elementary science. Question is what is the weight of electrons has been delivered from U.S. power stations today? strictly the answer is none. For AC current, electric field is reversed 50 times and hence no net flow of electrons. In DC current, same effect, electrons move backward and forward a very short distance without, on average, making overall shift in either direction. However, what you could count is the number of electrons that just enter and just leave the power station.

One electron can carry a charge of 1.6e-19 units of electrical charge (proved by Robert Millikan). An electric current of 1 amp is a flow rate of one unit of electrical charge each second; it is carried by 1/1.6e-19 = 6.24e18 electrons per second. A current of 1 amp running for 1 hour would transfer 6.24e18 x 3600 = 2.2e22 electrons. Daily consumption of electricity in U.S. is 11 billion kWh. If you divide this by voltage (electrical power = voltage x amps), you get average current of 200 million amps for 24 hours every day. The number of electrons that flow in a 1 amp for 1 hour is 2.2e22 electrons, so total daily electron flow to the nation is 2.2e22 x 200e6 x 24 = 1.05e32 electrons. One electron has a tiny mass of 9.1e-31kg. Now multiply mass times no. of electrons, i.e. 9.1e-31 x 1.05e32 = 96 kg – weight of big man.