We last learned about friction, the sort of ‘anti-force that prevents objects from achieving velocity. A more general topic of frictional forces that occurs when an object has achieved velocity is retarding forces and drag. Friction can be thought of as the minimal force required to get an object to move, but once it is moving, drag and other factors come into play that try and stop the object. These forces play an important role in things like gas mileage of a car and terminal velocity of falling objects. In some problems later on youll see there are two kinds of friction: static and kinetic. Static friction is the friction youve learned, or the ‘standstill friction, and drag is the kinetic friction, or the moving friction.
When the frictional force is a function of an object’s velocity, the frictional force is known as a drag, or retarding, force.
Typically we assume the drag force takes the form F=bv or F=cv^2, where b and c are constants.
Once an object reaches its maximum velocity, when the net force on the object is zero, we say the object has reached its terminal velocity.
To find velocity as a function of time, write your Newton’s 2nd Law equation in the form of a differential equation. Standard bodies falling through the air with air resistance can typically be solved using the method of separation of variables.
Retarding & Drag Forces
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This book includes a comprehensive review of the key AP Physics C concepts and targeted strategies for acing every section of the exam. Additionally, the book includes two full length practice tests with full answer explanations.
The book offers a complete review of your AP course, strategies to give you the edge on test day, and plenty of practice with AP-style test questions. It includes 2 full length practice exams modeled on the real test, 3 separate plans to fit your study stle, review material updated to the most recent tests, and all the terms and concepts you need to know.