Over 30yrs for me! I feel sorry for ciggys' generation. They haven't a clue how to start a problem like this, and yet they are supposed to be designing drill rigs .....
I'm trying to get my son with his yr 11 physics to take more notice of units as a check for the answer (if you end up with a velocity of 17kg per metre, you know you've gone wrong) but at his age it is natural to resist, based upon "they don't teach it like that in class".
