Fluids

Many types of race cars depend on negative lift (also called downforce) to push them down against the track surface so they can take turns quickly without sliding out into the track wall. Part of the negative lift on a car is due to one or more wings on the car, and in the wind tunnel photograph here, smoke released at the front of the car reveals how the air flows over the car and past the wing at the rear. The rest of the negative lift is called ground effect and has to do with the airflow beneath the car. Ground effect is dependable when a car is the only one taking a turn as in, say, a time trial, but a skilled driver knows that ground effect can disappear during a race.

What causes ground effect and why can it disappear?

The answers are in this lesson.

What Is Physics?

The physics of fluids is the basis of hydraulic engineering, a branch of engineering that is applied in a great many fields. A nuclear engineer might study the fluid flow in the hydraulic system of an aging nuclear reactor, while a medical engineer might study the blood flow in the arteries of an aging patient. An environmental engineer might be concerned about the drainage from waste sites or the efficient irrigation of farmlands. A naval engineer might be concerned with the dangers faced by a deep-sea diver or with the possibility of a crew escaping from a downed submarine. An aeronautical engineer might design the hydraulic systems controlling the wing flaps that allow a jet airplane to land. Hydraulic engineering is also applied in many Broadway and Las Vegas shows, where huge sets are quickly put up and brought down by hydraulic systems.

Before we can study any such application of the physics of fluids, we must first answer the question “What is a fluid?”