Two charges of # -2 C # and # 6 C# are positioned on a line at points # 3 # and # 4 #, respectively. What is the net force on a charge of # -5 C# at # 0 #?

1 Answer
Mar 5, 2017

Answer:

#6.9xx10^9N# attractive force.

Explanation:

The electrical force is given by

#F = k(Q_1Q_2)/r^2#

where #k ~~ 9xx10^9# is Coulomb's constant, #Q# is the charge and #r# is the distance between them.

The force between the #-2C# and #-5C# charges is

#F = 9xx10^9 xx (-2 xx -5)/3^2 = 10^10N#

and, between the #6C# and #-5C# charges, is

#F = 9xx10^9 xx (6 xx -5)/4^2 = -1.69 xx 10^10#

The net force is the sum of the forces, so

#F_("net") = 10^10 + (-1.69xx10^10) = -6.9xx10^9N#

This is in the negative direction, which is the same direction as the force between the #-5C# and #6C# charges, which must attract because the are opposites. Therefore, the net force is attractive, too.