Physics

Problem

Cities P and Q are

120\,\text{km}

apart along an east-west highway, with Q east of P. At

t=0

, Car 1 leaves P heading east at

25\,\text{m\,s}^{-1}

, and simultaneously Car 2 leaves Q heading west at

20\,\text{m\,s}^{-1}

. Twenty minutes after the cars pass each other, Car 3 departs from P heading east at

30\,\text{m\,s}^{-1}

. How long after its departure will Car 3 meet Car 2? a) About

17\,\text{min}

b) About

24\,\text{min}

c) About

14\,\text{min}

d) About

22\,\text{min}