Question

A bird is tossing (flying to and fro) between two cars moving towards each other on a straight road. One car has speed of $27km{h}^{-1}$ while the other has the speed of $18km{h}^{-1}$ . The bird starts moving from first car towards the other and is moving with the speed of $36km{h}^{-1}$ when the two cars were separated by $36km$ . The total distance covered by the bird is

• A. $28.8km$
• B. $38.8km$
• C. $48.8km$
• D. $58.8km$

Answer 1

Answer: (A)

Velocity of car $A$ , $v_A=+27km{h}^{-1}$
Velocity of car $B$ , $v_B=-18km{h}^{-1}$
Relative velocity of car $A$ with respect to car $B$
$=v_A-v_B+27km{h}^{-1}-\left(-18km{h}^{-1}\right)=45km{h}^{-1}$
Time taken by the two cars to meet $=\frac{36km}{45km{h}^{-1}}=0.8h$
Thus, distance covered by the bird
$=36km{h}^{-1}\times 0.8h=28.8km$