Automotive physics: Teaching students about inverse velocity forces and fast cars
DOI: 10.1063/10.0044344
Automotive physics: Teaching students about inverse velocity forces and fast cars lead image
Introductory physics students study many different forces, eventually developing a strong intuitive sense for them. However, more focus is given to dissipative forces than propulsive ones, and Chris Lin suggests the inverse velocity force, key to analyzing the limits of automotive performance, is a useful addition to the classroom.
“Propulsive forces are often ignored but are arguably more fun,” Lin said. “It’s more fun talking about a car speeding up than slowing down!”
The inverse velocity force represents the maximum force a power-limited engine can deliver at a specific velocity. At specific engine speeds, changing a vehicle’s gear to adjust its transmission changes its mechanical advantage, and understanding these relationships is vital for maximizing an engine’s power.
Aside from air resistance, students rarely study velocity-dependent forces; they are much more used to forces relying on position. Though it can be difficult for instructors to find time within often predetermined curricula to include additional content, Lin says the applications and distinctiveness of the inverse velocity force make it a good choice.
“Every instructor has a list of things they want to fill that small space with, so the biggest challenge is competing against all the interesting topics for lecture time,” he said.
The force can potentially be applied in other types of machinery, too, but its primary interest is in making cars go fast.
“Motorsports are as popular as ever,” Lin said, adding that understanding these forces remains relevant in the age of electric vehicles — though their transmission mechanism is different from gas engines. “They, too, undergo an inverse velocity force when set to go their fastest, so now seems especially a good time to bring some of these topics to the classroom.”
Source: “The inverse velocity force and automotive physics,” by Chris L. Lin, American Journal of Physics (2026). The article can be accessed at https://doi.org/10.1119/5.0278714 .
