The acceleration of a train between two stations 2 kilometre apart is shown in the figure. If train starts from rest than maximum speed of the train is

Options

A. `30ms^(-1)`
B. `60ms^(-1)`
C. `90ms^(-1)`
D. `120ms^(-1)`

Answer

D

Explanation

Magnetic moment `vec(M)` is along SN
`vec(B)_(P)=(mu_(0))/(4pi)(2vec(M))/(a^(3))=Bhat(i)` (Given)
`implies" "vec(B)_(Q)=(mu_(0))/(4pi).(2vecM)/(a^(3))=Bhat(i)` and
`vec(B)_(R )=(mu_(0))/(4pi).(vec(M))/(a^(3))=-(1)/(2)vec(B)hat(i)`