Speed: fast and slow Lesson 36 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 Speed is how far you go in a certain time: when the car's speedometer shows 50, the car would cover 50 kilometres if it kept that speed for a whole hour. 1 Moving things keep moving the way they are moving until something stops or turns them; this is called inertia, and it is why you lurch forward when the car brakes. 2 On a smooth train a ball you drop lands at your feet, because the ball was already moving along with the train and you. 3 To speed up, slow down or turn, you need a push: the engine pushes the car faster, the brakes slow it, and the ground pushes sideways on your feet when you turn. 4 A fast car carries much more energy than a slow one, so it needs a much longer way to stop, and that is why the speed limit outside a school is low. 5 Speed is how far something goes in a certain time; 50 kilometres an hour means 50 kilometres in one hour at that speed. 6 To compare speeds you need both the distance and the time; the winner of a race covers the distance in the least time. 7 A cheetah can sprint at about 100 kilometres an hour for a short time, while a snail takes a few minutes to go a metre. 8 Moving things keep moving the way they are going until something stops or turns them; this is inertia. 9 A ball dropped on a smooth train lands at your feet because it was already moving with the train. 10 When a car brakes, your body keeps moving forward; when it turns sharply, you lurch outwards. 11 A quick pull on a tablecloth can leave the dishes behind because they are slow to start moving, but a slow pull drags them with it. 12 A lighter car speeds up faster than a heavy lorry with the same engine. 13 At twice the speed, a car needs about four times the braking distance. 14 Before braking even starts, a driver needs a moment to see, think and press the pedal, and the car carries on at full speed meanwhile; a phone makes that moment longer. 15 A passenger plane flies at about 900 kilometres an hour, many times faster than a car, yet high in the sky it is so far away that it seems to crawl. 16 To turn, you need a sideways push from the ground on your feet, which is why footballers slip turning on wet grass. ← previous Pulleys, gears and big machinesnext → Seat belts, crashes and keeping safe↑ back to Physics This page in Markdown → https://md.mova.elamur.ai/free/en/corpora/school/physics/36-speed-fast-and-slow/