John Nichols, age 7, of Toronto, Ontario, Canada, for his question:
How much water falls over Niagara and how fast?
A driver steps down on the accelerator to speed up the car from 30 to 40 to 50 miles per hour. If the speeding car bashes head on into a brick wall, the force of the crash smashes it into a total wreck. The falls of Niagara hit the river below with more force than five million crashing cars.
Suppose we give an empty cup to each child .and grown up in the whole world. Then let's invite them all to behold the beauty of Niagara. The sight of all that plunging white water may make them thirsty. But Niagara spills enough to fill all their empty cups once every day. The amount of water is not always the same. In winter when the lakes are frozen, less water plunges over the two ledges. In spring, when the ice melts, extra water drains from the Great Lakes into the Niagara River and thunders over the falls. But every day there is enough tumbling water to fill a cup for everyone.
The Falls of Niagara are so stupendous that visitors never notice that sometimes there is more water and sometimes less. But experts must know how much to expect. Some of the force of the plunging torrents is used to run 1,500 electric power plants. So experts have figured how much water comes crashing over on an average minute. This average would be the amount of water if the falls were always the same. If the falls were measured every minute of the year, the average amount would be balanced in the middle.
Experts figure that Niagara spills about 500,000 tons of water in an average minute. A gallon of water weighs 8 1/2 pounds and there are 2,000 pounds in each of those tons of tumbling water. Niagara could fill more than 600 quart battles for each person in Toronto every minute. Or in about two minutes, the thundering, falls spill enough water to fill a tub for every Canadian.
Most of the torrent plunges over Canada's stupendous Horseshoe Falls. Likd a falling stone, it gathers speed on the way down. Each second it drops farther and faster. In the first second, it slides over the ledge and could attain a speed of up to 32 feet per second. Actually it drops about 15 feet. In the next second, it could speed up to as much as 64 feet per second. After three seconds, it is falling at close to 96 feet per second and should be about 140 feet down. After about four seconds, the trip is over. Half a million tons of water crash into the river at about 50 miles per hour.
Failing stones and water, feathers and raindrops are pulled down by the earth's gravity. This is the same force that hugs us to the surface of the globe. Gravity pulls down water and other falling objects at a fixed rate. And the rate accelerates, speeds faster 4~every second. Gravity tries to make a waterfall accelerate 32 feet per second with every second of falling time. This is a speed up of more than 20 miles an hour per second. But air and other things slow down gravity's acceleration. This is why Niagara splashes at 50 miles instead of 80 miles per hour.