Question

Two cars move in the same direction along parallel roads. One of them is a `200m`, long travelling with a velocity of `20m//s`. The second one is `800m` long travelling with a velocity of `7.5m//s`. How long will it take for the first car to overtake the second car?
A. `20s`
B. `40s`
C. `60s`
D. `80s`

Answer 1

(d) From the figure the relative disdplacement is

`s_("rel")=(800+200)m=1000m`
`v_("rel")=v_(1)-v_(2)=(20-7.5)m//s=12.5m//s`
`=(s_("rel"))/(v_("rel"))=1000/12.5=80s`