Question

Wind is blowing west to east along two parallel tracks. Two trains moving with same speed in opposite directions have the relative velocity w.r.t. wind in the ratio 1 : 2. The speed of each train is

(a) equal to that of wind

(b) double that of wind

(c) three times that of wind

(d) half that of wind

Answer 1

Correct option (c) three times that of wind

Explanation:

Let v be velocity of wind and u be velocity of each train.

Rel. vel. of one train w.r.t. wind = 2 × Rel. vel. of other train w.r.t. wind

u + v = 2(u – v)

v + 2v = 2u – u = u.

i.e., u = 3v.