Look this link http://www.convertworld.com/en/speed/

5 m/s = 18 km/h
20 m/s = 72 km/h

I just do it in my head.

25m/s = 50mph = 80kmh
10m/s = 20mph = 35kmh

mph is roughly double m/s, and km/h is roughly half of mph again plus a bit. Quite easy to results accurate enough.

Wow... people must be getting REALLY lazy.

more exact values
10 m/s = 10 * 3.6 = 36 km/h
36 / 1.6 = 22.5 mp/h

I think the speed displayed on speedos in cars should be in m/s from now on. It will cause some awareness of how fast you are actually going. 100kmh doesnt sound that fast, but 28 m/s does. Especially if you are 2m behind the car in front. That means that you are only 0.07 seconds behind him.

Oh, and I think about everyone that managed to pay attention at physics class knows the conversion factor for kmh to m/s and mph to kmh.

Quote from Frankmd :

100kmh doesnt sound that fast, but 28 m/s does.

It's the opposite for me, I have no idea how fast I'm going in m/s and since the values are smaller it just doesn't click that 40 m/s would be particularly fast..

If you have ever done any sort of running you would appreciate how fast that is

Quote from Frankmd :

I think the speed displayed on speedos in cars should be in m/s from now on. It will cause some awareness of how fast you are actually going. 100kmh doesnt sound that fast, but 28 m/s does. Especially if you are 2m behind the car in front. That means that you are only 0.07 seconds behind him.

when your are THAT close to the car in front you don't really care how fast you are going i think, it's more like you are fighting for a position and you simply don't have time to look at the speedo

I was refering more to the situation on our highways nowadays. People are so close behind each other, they really dont have any sense of how close it actually is.

Quote from sil3ntwar :

If you have ever done any sort of running you would appreciate how fast that is

Running? Me? Don't be silly, that's physical exercise isn't it..

100m in 10s is 10 m/s, I'd like to think I'm moving a fair bit faster than a 100m sprinter in my race-prepped GTR