Passenger kinematics

This post builds on the post Physics for travelers. Passengers are travelers or riders with a specific destination.

In a way passengers are passive; they just sit as a vehicle takes them where they want to go. But that comes after they entered the vehicle, which comes after they accepted a ride or bought a ticket, which comes after they decided to go on a trip, which comes after they chose a destination. There’s much activity before (and after) a passenger sits.

A passenger may decide to operate a vehicle themselves as the biker, the driver, the pilot. Even then they are passengers first and operators second, unless they are in the transportation business.

The passenger perspective may be explained by the four causal factors: (1) the passenger determines the destination of their trip; (2) the passenger decides on the mode and manner of their trip; (3) the passenger decides on the means of their trip, such as which route and vehicle; (4) the passenger decides the who and when and what of the trip.

The destination is a place that is different from the place where the passenger begins. Children who sit in a car and pretend they are going somewhere are not passengers. Passengers first need is a destination.

The physics of most interest to passengers is not the physics of an engine or of someone else’s transport but of their own transport to their own destination. That is, the physics of most interest is the physics of closing the gap between them and their destination. Passengers begin with a positive distance between them and their destination, which they want reduced to nothing.

Consequently, the independent variable for passengers is a distance, not a time interval. Time is always a dependent variable for passengers. This differs from the physics of scientists and engineers for whom time is the independent variable as they observe and design things in motion.

This leads to the rate of motion for passengers being measured in the amount of time taken (duration) per unit of length traversed. This is called the pace in racing, in which the travel time is minimized. Passengers may be in a race, or may simply have a deadline for reaching their destination. A slower pace means a larger amount of time passing per unit distance. A faster pace means a smaller amount of time passing per unit distance.

What about the increase or decrease in the rate of motion? For passengers this is a change in the pace toward either a faster or slower pace. A slow pace getting slower means an increasingly large amount of time passing per unit distance. A fast pace getting faster means a decreasingly small amount of time passing per unit distance. That is, rate of change of the rate of change is the change of pace distance over which the change is measured.

Consider a passenger on a trip with several signposts that are equally spaced (to make it simple). One can measure the time it takes to pass each signpost and determine whether the time is getting larger or smaller. The independent variable is again the travel distance but it covers the distance of the two paces. The faster the change in pace, the smaller the amount of time per unit distance. The slower the change in pace, the larger the amount of time per unit distance.

The background to these measures is that the passenger would like arrive instantly at their destination, so any time passing until their arrival is viewed adversely. Larger numbers mean slower movements. Smaller numbers mean faster movements. This is the opposite to thinking that larger numbers mean faster movements.

Relentation means the change in pace or lenticity, which means motion will go slower. Derelenetation is the negative of relentation; it means the change in pace or lenticity such that motion will go faster. Retardate means to decrease the pace or lenticity and go faster. Deretardate means to increase the pace or lenticity and go slower. Unrelentated means the relentation is zero.