An attractive force of 7.2 N occurs between two point charges that are 0.10 m apart. If one charge is 4.0 µC, what is the other charge? (µC = 1.0 × 106 C)

(Points : 3)
1.0 µC

2.0 µC

+1.0 µC

+2.0 µC

Which substance is most easily grounded?
(Points : 3)
plastic foam plate

copper rod

rubber tire

PVC pipe

1 answer

F=kq₁q₂/r²
q₂= F r²/kq₁= 7.2•10⁻²/9•10⁹•4•10⁻⁶=
=2•10⁻⁶ C = 2μC

Cpper rod is an electrical conductor; the others are insulators.