John is entering Steward, and drives West, with a Uav of 88 km/h.
He arrives at Aurora, and realises he took a wrong turn.
He turns around and drives East, towards York, with a Uav' of 79 km/h.
Steward-Aurora is 76 km & and Aurora-York is 34 km.
For the whole trip (S -> A -> Y) find:
a) What's the average metre (meaning the positive value of a quantity, eg | -70| = 70) of his speeds (U)?
b) What's the metre of his average speed?
Uav = (Xfinal - Xstarting)/(tfinal - tfirst)
The Attempt at a Solution
S->A: [/B]Ssa = |Usa|*tsa <=> 76 km = 88 km/h*tsa <=> tsa = 0,86h
A->Y: Say = |Uay|*tay <=> 34 km = 79 km/h*tay <=> tay = 0,43 h
Sc = (76 + 34) km = 110 km
tc = (0,86 + 0,43) = 1,29 h
- Okay, so, the answers are:
a) 85 km/h
b) 32 km/h
Personally, I think he got them mixed up. The metre of his average speed (b) if I'm not mistaken, should be: |Uav| = Sc/tc = 110 km/ 1,29 h ~ 85 km/h
So, it's just a typo, right? Well, thing is, for the life of me, I can't understand what question (a) means. I translated it here as well as I could. So, any ideas?
Any kind of help would be appreciated!