Question

Two point charges q1=20c and q2=25 c are placed at (-1,1,1)m and (3,1,-2)m with reapect to some coordinate axis.find magnitude and unit vector along force on q2

Answer 1

Let position vector of q1 is r1 and position vector of q2 is r2

e.g., r1 = (-1, 1, 1) and r2 = (3, 1, -2)

we have to find magnitude and unit vector along force on q2.

so, position vector of q2 with respect to q1 , r = r2 - r1 = (3, 1, -2) - (-1, 1, 1) = (4, 0, -3)

magnitude of r = |r| = √{4² + 0² + (-3)²} = 5

magnitude of force on q2 = kq1q2/|r|²

= 9 × 10^9 × 20 × 25/5²

= 9 × 10^9 × 20

= 1.8 × 10¹¹ N

now, unit vector along force on q2 = (r2 - r1)/|r2 - r1| = (4, 0, -3)/5 = (0.8, 0, -0.6)

hence, unit vector is (0.8, 0, -0.6)