Three charges lie on a straight line. A +4.0μC charge is at x=0, a +1.0μC charge is at x=0.30m, and a −2.0μC charge is at x=0.80m. Determine the net electrostatic force on the +1.0μC charge.
The +4.0μC charge repels the middle charge to the right:
FL=0.302k(4.0×10−6)(1.0×10−6)=0.400N.
The −2.0μC charge attracts it to the right:
FR=0.502k(2.0×10−6)(1.0×10−6)=0.0719N.
Both forces act right, so
Fnet=0.400+0.0719=0.472N.
Determines force from left charge.
[1 mark]
Determines force from right charge.
[1 mark]
Identifies both directions correctly.
[1 mark]
Adds to obtain net force.
[1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.