Point Particle Dynamics

Introduction to the Model

Description and Assumptions

This model is applicable to a point particle (or to a system of objects treated as a point particle located at the system's center of mass) when the external forces are known or needed. It is a subclass of the model Momentum and External Force defined by the constraint dm/dt = 0.

Learning Objectives

Students will be assumed to understand this model who can:

• State and explain the significance of Newton's Laws of Motion.
• Define normal force and describe its relationship to weight.
• Discriminate between static and kinetic friction.
• Explain the role of the coefficient of friction in both the kinetic and static cases.
• Construct a free body diagram for an object subject to contact forces, gravity, elastic forces, and/or tension forces.
• Construct and solve a system of equations describing the dynamics of more than one object that interact with one another.

S.I.M. Structure of the Model

Compatible Systems

A single point particle, or a system of constant mass that is treated as a point particle located at the system's center of mass.

Relevant Interactions

External forces must be understood sufficiently to draw a free body diagram for the system. Internal forces will always cancel from the equations of Newton's 2nd Law for the system and can be neglected.

Law of Change

Mathematical Representation

As with all vector equations, this Law of Interaction should really be understood as three simultaneous equations:

Diagrammatical Representations

• Free Body Diagram

Relevant Examples

Examples Involving Vector Components

Examples Involving Normal Force

Examples Involving Apparent Weight

Examples Involving Tension

Examples Involving Inclined Planes

Examples Involving Static Friction

Examples Involving Kinetic Friction

Examples Involving Centripetal Acceleration

All Examples Using this Model

Photos courtesy:
US Navy by Mass Communication Specialist 3rd Class James R. Evans

US Army by Spc. Michelle Waters