Free Body Diagrams Unit V – Newton’s Laws of motion
Drawing Free Body Diagrams A diagram used to show the relative magnitude and direction of all forces acting upon an object in a given situation. It is a vector diagram The size of the arrow reflects the magnitude of the vector. The direction of the arrowhead reflects the direction the force is acting in To draw a free body diagram you must depict all of the forces that exist for that object in a given situation.
Drawing free body diagrams Example: An egg is free falling from a nest in a tree. Neglect air resistance. Diagram the forces acting on the egg as it is falling. A rightward force is applied to a book in order to move it across a desk with a rightward acceleration. Consider frictional forces. Neglect air resistance. Diagram the forces on the book.
Drawing free body diagrams A football is moving upwards towards its peak after having been booted by the punter. Diagram the forces acting upon the football as it rises upward towards its peak.
Determining Net forces Unbalanced forces are forces that do not become completely balanced by other forces. The diagrams below illustrate unbalanced forces. Images from the Physics classroom
Determining Net forces The net force is the vector sum of all the forces action upon the object. Examples of summing vector forces: Images from The Physics Classroom
Determining Net forces Using the examples below determine the net force acting on each example:
Net forces cause acceleration Is there acceleration based on the following images: Image AImage B Images from The Physics Classroom
Free Body Diagram problem: Free-body diagrams for four situations are shown below. The net force is known for each situation. However, the magnitudes of a few of the individual forces are not known. Analyze each situation individually and determine the magnitude of the unknown forces. Images from The Physics Classroom
Works Cited The Physics Classroom. (2013). Newton’s Laws – Lesson 2. Retrieved from newtlaws/u2l2d.cfm newtlaws/u2l2d.cfm