1. First, invest in a spare inner tube. If you get a puncture on the road it's far easier to change the tube and repair the punctured one later at home. To repair the tube you'll need a pump, tyre levers and a puncture repair kit with patches, sandpaper, a marker and glue.
Mass is a measure of the number of atoms in an object combined with the density of those atoms. Usually people measure mass in kilograms. You can tell how much mass something has by measuring how hard it is to get that thing to change directions or slow down. If you're driving a big truck, for instance, you're going to need a lot stronger brakes to stop the truck than if you were riding a bicycle.
Mass[edit] Mass is the measure of inertia. From a subatomic point of view, mass can also be understood in terms of energy, but that does not concern us when dealing with chemistry. Mass for particles, atoms, and molecules is not measured in grams, as with ordinary substances. Instead, it is measured in atomic mass units, or amu.