Particle

Goals

1. Describe a particle.

2. Skillfully model objects as particles.

What?

A particle is a model (simplified version) of a physical object that involves treating the object as if it has mass but no size or shape.

Examples

An airplane moving at 400 km/hr in straight and level flight is typically modeled as a particle.

A ball flying through the air can be treated as a particle if you’re only interested in its path, not how it spins.

A satellite orbiting Earth can be modeled as a particle when analyzing its trajectory.

In statics, a point on a structure where multiple cables connect can be treated as a particle to analyze force balance.

Why Learn This

1. Modeling physical objects as particles is commonly used in engineering practice.

2. When you model an object as a particle, the analysis is much simpler than if you select a different model such as a rigid body, or system of particles.

3. Modeling, which is the process of creating a simplified version of reality, is so useful that it can be considered as an engineering superpower.

4. Particle models are applied in multiple engineering subjects including Statics, Dynamics, and Fluid Mechanics.

Skillful Application of Particles

Model an physical object as a particle iff (if and only if), its size and shape can be neglected.

When a physical object is modeled as a particle, there cannot be an moments (torques) that are relevant.

The following scientific la are used for modeling particles.

$$\sum \vec{F} = \vec{0} \iff \vec{a} = \vec{0}$$