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Question Number 17689 by Tinkutara last updated on 09/Jul/17
A bird is tossing (flying to and fro)  between two cars moving towards  each other on a straight road. One car  has a speed of 18 km/h while the other  has the speed of 27 km/h. The bird  starts moving from first car towards  the other and is moving with the speed  of 36 km/h and when the two cars were  separated by 36 km. What is the total  displacement of the bird?
$$\mathrm{A}\:\mathrm{bird}\:\mathrm{is}\:\mathrm{tossing}\:\left(\mathrm{flying}\:\mathrm{to}\:\mathrm{and}\:\mathrm{fro}\right) \\ $$$$\mathrm{between}\:\mathrm{two}\:\mathrm{cars}\:\mathrm{moving}\:\mathrm{towards} \\ $$$$\mathrm{each}\:\mathrm{other}\:\mathrm{on}\:\mathrm{a}\:\mathrm{straight}\:\mathrm{road}.\:\mathrm{One}\:\mathrm{car} \\ $$$$\mathrm{has}\:\mathrm{a}\:\mathrm{speed}\:\mathrm{of}\:\mathrm{18}\:\mathrm{km}/\mathrm{h}\:\mathrm{while}\:\mathrm{the}\:\mathrm{other} \\ $$$$\mathrm{has}\:\mathrm{the}\:\mathrm{speed}\:\mathrm{of}\:\mathrm{27}\:\mathrm{km}/\mathrm{h}.\:\mathrm{The}\:\mathrm{bird} \\ $$$$\mathrm{starts}\:\mathrm{moving}\:\mathrm{from}\:\mathrm{first}\:\mathrm{car}\:\mathrm{towards} \\ $$$$\mathrm{the}\:\mathrm{other}\:\mathrm{and}\:\mathrm{is}\:\mathrm{moving}\:\mathrm{with}\:\mathrm{the}\:\mathrm{speed} \\ $$$$\mathrm{of}\:\mathrm{36}\:\mathrm{km}/\mathrm{h}\:\mathrm{and}\:\mathrm{when}\:\mathrm{the}\:\mathrm{two}\:\mathrm{cars}\:\mathrm{were} \\ $$$$\mathrm{separated}\:\mathrm{by}\:\mathrm{36}\:\mathrm{km}.\:\mathrm{What}\:\mathrm{is}\:\mathrm{the}\:\mathrm{total} \\ $$$$\mathrm{displacement}\:\mathrm{of}\:\mathrm{the}\:\mathrm{bird}? \\ $$
Answered by mrW1 last updated on 09/Jul/17
((36)/(27+18))×36=28.8 km
$$\frac{\mathrm{36}}{\mathrm{27}+\mathrm{18}}×\mathrm{36}=\mathrm{28}.\mathrm{8}\:\mathrm{km} \\ $$
Commented by mrW1 last updated on 09/Jul/17
I misread the question. The cars move  towards each other, not in the same  direction as I understood. The answer  is corrected.
$$\mathrm{I}\:\mathrm{misread}\:\mathrm{the}\:\mathrm{question}.\:\mathrm{The}\:\mathrm{cars}\:\mathrm{move} \\ $$$$\mathrm{towards}\:\mathrm{each}\:\mathrm{other},\:\mathrm{not}\:\mathrm{in}\:\mathrm{the}\:\mathrm{same} \\ $$$$\mathrm{direction}\:\mathrm{as}\:\mathrm{I}\:\mathrm{understood}.\:\mathrm{The}\:\mathrm{answer} \\ $$$$\mathrm{is}\:\mathrm{corrected}. \\ $$
Commented by Tinkutara last updated on 09/Jul/17
It is the total distance, not displacement.
$$\mathrm{It}\:\mathrm{is}\:\mathrm{the}\:\mathrm{total}\:\mathrm{distance},\:\mathrm{not}\:\mathrm{displacement}. \\ $$
Commented by mrW1 last updated on 09/Jul/17
displacement = ((36)/(27+18))×18=14.4 km
$$\mathrm{displacement}\:=\:\frac{\mathrm{36}}{\mathrm{27}+\mathrm{18}}×\mathrm{18}=\mathrm{14}.\mathrm{4}\:\mathrm{km} \\ $$
Commented by Tinkutara last updated on 09/Jul/17
Yes, Thanks Sir!
$$\mathrm{Yes},\:\mathrm{Thanks}\:\mathrm{Sir}! \\ $$

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