On a 200 km bike cycle ride, you ride the first 90 km at an average speed of 20 m/s. What must your average speed over the next 40 km be to have your average speed for the total 200 km be?
(a) 60 m/s?
(b) Given this average speed for the first 90 km, can you possibly attain an average speed of 80 m/s for the total 200 km ride? Explain .
- ?Lv 71 month ago
(a) The elapsed time to go the first 90 km is
(90000 m)/(20 m/s) = 4500 s.
To attain an average speed of 60 m/s for the whole 200 km, the total elapsed time must be no more than
(200000 m)/(60 m/s) = 3333 s.
There is no way you can catch up, you already used up too much time in the first 90 km.
(b) Ditto, you already used up too much time in the first 90 km.