Three particles `A,B` and `C` and situated at the vertices of an equilateral triangle `ABC` of side of length `l` at time `t=0`,Each of the particles move with constant speed `u`. A always has its velocity along `AB, B` along `BC` and `C` along `CA`.

Options

A. The time after which they meet is `(2l)/(3u)`
B. Total distance travelled by each particle before they meet is `(2l)/3`
C. Average velocity during the motion is `(sqrt3u)/2`
D. Relative velocity of apporach between any two particles is `(3u)/2`

Answer

A, B, C, D

Explanation

`t=l/u_(rcl)=1/(u+u/2)=(2l)/(3u)`
Distance `=intvdt=uxx(2l)/(3u)=(2l)/3`
`v_(avg)="total disp"/"total time"=((l)/(sqrt(3)))/((2l)/(3u))=sqrt(3u)/2`
`V_(AB)=u+u cos 60=(3u)/2`