Tuesday, April 24. 2018Who invented the parachute?
Leonardo de Vinci (1452-1519) was thought until recently to have been the first to design a parachute. But drawings have now been found that were made five years before da Vinci’s sketches, possibly by an engineer in Siena central Italy. However, the first man to make and successfully use a parachute was a Frenchman, Andre Garnerin (1770-1825), who stretched cloth across a bamboo framework and parachuted from a balloon over Paris in 1797. It was an uncomfortable descent as the fabric was too thick o spill out any wind, and the parachute came down swinging violently like a pendulum. Garnerin was is a tiny basket, to which he clung tightly until his rough landing on the plain of Monceau. The parachutes of those days were developed from the crude canvas devices used to descend from hot air balloons. Modern parachutes are made of pure silk or good-quality nylon in small panels and have a small pilot parachutes which open first and helps to pull out the main parachute. Picture credit: google Tuesday, April 24. 2018Why does smoke go up the chimney?
Smoke will rise up the chimney or through the nearest opening it can find because it is hotter and, therefore, lighter than the air in the room. Before the days of chimneys smoke was allowed to escape through vents or open turrets in the roof. Chimneys were introduced to induce a draught, thus providing more air for the fire. The hot smoke passing up the shaft made room for cool air, of higher density. Thus a chimney would not only carry away the smoke and gases from a fire but also act as a ventilator enabling a change of air in the room. Picture credit: google Tuesday, April 24. 2018How do drink-vending machines work?
Drink-vending machines are operated electronically when coins are inserted and a button pressed to select the beverage required. They have four basic units, or a module on the inside of the cabinet door is the electrical unit where the dispensing of a drink is programmed through the other three-the cupper dispenser, the recirculating water system and the ingredient container units. When the coins are put into the slot, they are checked by an electronic scanning unit. If they are checked by an electronic scanning unit. If they are the wrong coins they are rejected. If accepted, they set off the programme. The release mechanism of the dispenser allows a cup to fall down a chute to the service position. While this is happening, a portion of the selected ingredient in powder from is released from its container into a large mixing bowl that looks like a big flattish funnel. Here hot water is added to dissolve the powder and the resulting beverage is poured into the waiting cup. Finally more water enters the mixing bowl, which is then automatically cleaned in readiness for the next customer. Picture credit: google |
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