 Now there are enormous number of different SI units and that's just a small sample of them So don't be surprised if you don't recognize some of these when there are many others besides you almost certainly recognize the second and the kilogram and the vault and the Hertz and the meter or The ohm maybe and the Newton But maybe you haven't heard of the Weber and perhaps there's no surprise There's such a large number of units and remember This is just a subset because there's such a large number of different things We might want to measure the weight of a swimming pool the height of a tree the pressure under a shoe heel the conductance of a nerve Speed of a bicycle the brightness of a star maybe the wind velocity of course two of those the same So the speed of a bicycle and the wind velocity are both velocities in other words You both measure them in terms of distance over time Now one of the things that's done right in the metric system is that when you have a unit of velocity It's not a completely independent thing from the units of distance and time So we already have a unit of distance in the SI system and that's the meter And we already have a unit for time And so the conversion becomes very simple when the SI unit for velocity is indeed the meter per second