FULL STOP AHEAD
1) I think the estimates of speed do not double when the skid marks double in length is because of the road conditions.
2) Safe distances between cars changes based on whether the road is dry or wet.
After viewing the previous chart on activity 1, you see that 150 is between 40 and 50. I guessed and checked while doing this activity and discovered that 47 is the maximum speed you should be traveling in order to leave a safe stopping space.