Given :
Force on object moving with constant velocity due to magnetic field is given by :
[tex]\vec{F}=q\vec{v}\times \vec{B}\\\\\vec{F}=-5[ ( \hat{i} + 7\hat{j}) \times ( 10\hat{k})]\\\\\vec{F}=-5[ 10(-\hat{j})+70(\hat{i})]\\\\\vec{F}=50\hat{j}-350\hat{i}\ N[/tex]
Now,
[tex]F = \sqrt{50^2+350^2}\\\\F=353.55\ N[/tex]
Hence, this is the required solution.
