I travel about 11 meters per second at 40 km/h.

There are 3600 seconds in an hour. To convert from km/h into m/s, you divide the speed in km/h by 3.6. Conversely, if you are converting from m/s into km/h, you multiply by 3.6.

If you are driving at 40 km/h, this is the same as driving about 11 meters per second (40/3.6 is approximately equal to 11).

At 90 km/h you travel about 25 meters in one second. With a reaction distance of 25 meters, it is impossible to get a stopping distance (reaction distance + braking distance) of 30 meters.

Braking distance changes with the square of the change in speed, so if the braking distance is 5 meters at 25 km/h, it is 20 meters at 50 km/h. Braking distance changes with the square of the change in speed, so if the braking distance is 5 meters at 25 km/h, it is 20 meters at 50 km/h.

If you are driving at 70 km/h, you are travelling at about 19 meters per second. If you are driving at 70 km/h, you are travelling at about 19 meters per second.