Modeling a Body as a Particle

Goals

1. Explain what it means to model a body as a particle.
2. Skillfully do this.

What?

In mechanic (branch of physics), objects in the real world like tanker truck, gear mechanisms, buildings, the human body and so on are modeled as particles, rigid bodies, and as systems-of-particle.

A model is a simplified version of reality that is typically created because it is useful in the sense of giving us better results, time savings, or similar.

When an object or body is modeled as a particle, we imagine that all the mass can be concentrated at one point (typically the center-of-mass) and we can neglect the size and shape of the object.

Example

For example, if a jet might be modeled as shown in the next sketch.

The jet is modeled as a particle with four forces acting it. If the jet is traveling at constant velocity in a straight line, then the lift force will balance the weight and the drag force will balance the thrust force.

Imagine a car moving up a hill.