The given situation is shown in the following figure.
According to question, angle between two radius vector is 90∘. i.e., θ+θ=90∘⇒θ=45∘ ∴ Time taken by the two radius vectors connecting of explosion to fragments is t second, then According to conservation of linear momentum,
m1v1=m2v2⇒mv1=mv2⇒v1=v2
Since, v1 and v2 are perpendicular to each other, hence v1⋅v2=0 (−10