--- title: Living with friction: oil, wheels and grip — a lesson of Mova's school · trees and pragmatics description: «Living with friction: oil, wheels and grip», a lesson of the physics course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: To make it smaller, we put oil between rubbing parts, or we use wheels and ball bearings so that things roll instead of rub. --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [Physics](https://md.mova.elamur.ai/free/en/corpora/school/physics/) / Living with friction: oil, wheels and… # Living with friction: oil, wheels and grip Lesson 7 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](https://md.mova.elamur.ai/free/en/school-run/physics/7-living-with-friction/). - [1](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/1/) — To make it smaller, we put oil between rubbing parts, or we use wheels and ball bearings so that things roll instead of rub. - [2](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/2/) — To make it bigger, we use rubber, chalk and rough surfaces: try opening a stuck jar with a rubber glove and it turns at once. - [4](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/4/) — Oil on a squeaky hinge makes a slippery layer between the metal parts, so they slide instead of rubbing. - [5](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/5/) — Car engines need oil; without it their metal parts would rub, heat up and seize (jam solid). - [6](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/6/) — Wheels roll instead of rub, so a suitcase on wheels moves easily, and before wheels people rolled huge stones on logs. - [7](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/7/) — Ball bearings are tiny steel balls that roll between a wheel and its axle, and they are in skateboards, bikes, fans and washing machines. - [8](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/8/) — Climbers and gymnasts put chalk on their hands because it soaks up sweat, and dry skin grips better than sweaty skin. - [9](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/9/) — A rubber glove helps open a jar because soft rubber moulds into the tiny bumps on the lid and grips it. - [10](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/10/) — Running a metal jar lid under hot water also helps, because the metal grows a little. - [11](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/11/) — Two books with their pages interleaved (slid in between each other, one by one) are almost impossible to pull apart, because the small grips of hundreds of pages add up. - [12](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/12/) — On a TV show, two interleaved phone books could not be pulled apart even by two cars. - [13](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/13/) — A spacecraft coming home glows red hot mostly because the air in front is squeezed and heats up, so it needs a heat shield. - [14](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/14/) — Fish are slippery because their skin is covered in slime, which also protects them from germs, so wet your hands before holding one. - [15](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/15/) — Once a tyre slides, it grips less than when it rolls, which is why a spinning tyre screeches and good drivers start smoothly. - [16](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/16/) — A ruler on a tilted desk starts to slide only when the slope is steep enough for gravity to beat friction, and a rubber eraser needs a much steeper slope. - [17](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/17/) — Knots in laces hold only because the lace rubs on itself. - [18](https://md.mova.elamur.ai/free/en/corpora/school/physics/7-living-with-friction/18/) — A banana skin is slippery because its squashed inside makes a slimy layer between your shoe and the floor. - ← previous: [Friction: the grip that stops and helps](https://md.mova.elamur.ai/free/en/corpora/school/physics/6-friction-the-grip/) - next →: [Balance: the centre of gravity](https://md.mova.elamur.ai/free/en/corpora/school/physics/8-balance-the-centre-of-gravity/) - ↑ back to [Physics](https://md.mova.elamur.ai/free/en/corpora/school/physics/)