You drive a car for 2.0 h at 40 km/h, then for another 2.0 h at 60 km/h.?

Question

a. What is your average velocity?


b. Do you get the same answer if you drive 1.0 × 10² km at each of the two speeds?

Answer 1

OK!
a.
How far total?
(40 * 2) + (60 * 2) = 200 km
How much time total?
2 + 2= 4hr

So the average velocity for the whole trip is:
200km/4hr = 50 km/hr

b.
(100 km * hr/40km) + (100km * hr/60km) =
2 1/2 + 1 2/3... hr =
4 1/6 hr

200 km/ (4 1/6 hr) = 48 km/hr

So, *no*.

EDIT: I really can't stand it when people say *yes* when the answer is *no*.

Answer 2

distance travelled in first 2 hrs=80kms
distance travelled in next 2 hrs=120kms
total distance travelled=200km
total time=4hrs
therefore average speed=50km/hr

b)u travel 40 km in 1hr therefore 100 km will be travelled in 100/40=2.5hr
60 km in 1hr therefore in 100/60or 5/3 hr u travel 100 km
total time = 2.5+1.67=4.17 hr
total distance=200 km
therefore average velocity is 200/4.17=48km/hr(ans)

Answer 3

A. (80+120)/4=50 KM/H
B. no 200/(2.5+1.666)<50