Two charges of # -1 C # and # -3 C# are positioned on a line at points # -2 # and # -4 #, respectively. What is the net force on a charge of # -3 C# at # 1 #?

1 Answer
Dec 30, 2015

Answer:

#0.8k# units

Explanation:

Click here for the diagram:

http://tube.geogebra.org/student/m2356805

The resultant force will be the vector sum of the forces due to the other two particles.

#stackrel(rarr)(F_("res"))=stackrel(rarr)(F_(31))+stackrel(rarr)(F_(32)#

Using Coulomb's Law:

#stackrel(rarr)(F_(31))=k.(3xx3)/(5^2)=(k.9)/25#

#stackrel(rarr)(F_(32))=k.(2xx2)/(3^2)=(k.4)/9#

#:.stackrel(rarr)(F_("res"))=(k.9)/25+(k.4)/9#

#stackrel(rarr)(F_("res"))=k0.8#

If the units of length were in metres then #k=9xx10^(9)"m/F"# and the result would be in Newtons.

The +ve sign means the force acts in the +ve direction i.e left to right.