AP Physics 2: Algebra-Based Unit 10 Topic 4: Electric forces and free-body diagrams

What to Know

Electric force direction depends on charge signs and field direction.
A free-body diagram should show forces acting on one selected object only.
Net force determines acceleration, even when one of the forces is electric.
Always connect this topic back to the larger unit: Electric Force, Field, and Potential.

Detailed Notes

Electric forces and free-body diagrams belongs to Unit 10: Electric Force, Field, and Potential. Electric forces can be included in free-body diagrams just like contact forces and gravity. Start by identifying the system, the field or interaction involved, and which conservation law or model applies.

Key relationships: Electric force direction depends on charge signs and field direction. A free-body diagram should show forces acting on one selected object only. Net force determines acceleration, even when one of the forces is electric.

Model to use: Draw the object of interest, then add electric, gravitational, tension, or normal forces as labeled vectors. A clear AP Physics 2 model should label directions, signs, units, and the physical meaning of each variable.

AP-style move: Use Coulomb's law or electric field force only after identifying the charge experiencing the force. For free-response work, show the governing principle first, then connect the mathematical result back to the physical situation.

Key Vocabulary

Electric force

A force on a charged object due to another charge or electric field.

Coulomb force

The electric interaction between point charges.

Charged-particle free-body diagram

A force diagram for a particle that includes electric forces.

Test charge

A small positive charge used to define or measure an electric field.

Force superposition

Vector addition of forces from multiple interactions.

Quick Practice

How would you explain Electric forces and free-body diagrams in one or two AP-style sentences?

Name the concept, apply it to a specific example or source, and explain the reasoning that connects the evidence to your answer.

Official Alignment

Reference and Attribution

AP Physics 2 concept reference: AP Physics 2: Concise Summary Notes by IITian Academy. EduCompanion used this source as a topic checklist and conceptual reference, then rewrote the study notes in original wording.

AP Physics 2: Concise Summary Notes