There’s a big branch on the pavement. Slow down your bike! Then you can go around the branch safely.
Your bike has brakes to help it stop. When you squeeze the levers on the handlebars, the brake pads rub against the wheels and stop them from turning. The rubbing that stops the wheels is called friction.
Friction happens because all things have a rough surface. Even things that look shiny and polished have very tiny areas that are not smooth. When one object slides across another, the rough spots rub against one another. This rubbing, or friction, makes things move more and more slowly, until finally they stop.
Friction is useful when it helps you stop your bike. But sometimes we want things to keep moving smoothly. Then we need to lessen friction. We can do this with a slippery substance, such as oil or grease. For example, the grease on your bicycle chain lessens friction so that you can pedal easily and smoothly.
Picture Credit : Google