Swings and pendulums Lesson 10 of the physics course of Mova's primary school: 17 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: the lesson at school .
0 A swing is a pendulum: a weight hanging from a point, going back and forth with its own steady rhythm. 1 Its rhythm is set by the length of the chains, not by how hard you are pushed or how heavy you are, which is why an old grandfather clock can count time with a swinging pendulum. 2 On the way down a swing turns height into speed, and on the way up it turns speed back into height, while the air and creaky chains slowly steal a little each time. 3 Pushes that come in time with the rhythm add up: that is how you pump yourself higher, and why marching soldiers break step on a bridge. 4 After one push a swing goes back and forth lower and lower until it stops, because air and the creaking chains take away its energy. 5 Moving your legs and leaning at the right moments adds a little energy each swing; kicking at the wrong moments slows you down. 6 For swings that are not too big, a big push and a small push give almost the same time for one back-and-forth. 7 Galileo noticed this watching a swinging lamp in a cathedral, timing it with his pulse. 8 A short pendulum swings quickly and a long one slowly; one four times as long takes twice as long to swing. 9 A heavy child and a light child on the same swing take the same time to go back and forth. 10 A grandfather clock counts the swings of its pendulum, and clockmakers move a little weight up or down to make it run faster or slower: moving it up makes the pendulum shorter, so the clock runs faster. 11 At the top of a swing you stop for an instant and feel almost weightless; at the bottom you feel heaviest, because the swing pulls you round the curve. 12 A swing is fastest at the bottom and slowest at the top, and a roller coaster swaps height and speed the same way. 13 Pushes that match something's own rhythm build up; a London footbridge wobbled on its first day in 2000 because walkers fell into step with its sway. 14 A wrecking ball gets its power from its height and weight, and it can swing back, so the area is cleared of people. 15 In Newton's cradle, swing one ball in and one flies out the other side, swing two in and two fly out, because the knock passes through the still balls. 16 A wine glass sings when you rub its rim with a wet finger, because the finger sticks and slips in time with the glass's own wobble; more water makes the note lower. ← previous Riding a bike: why it stays upnext → Floating and sinking: the push of the water↑ back to Physics This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/physics/10-swings-and-pendulums/