Mechanical engineeringLesson 2 of 4 in the course Statics

Free-Body Diagrams: Isolation, Modeling, and Force Analysis

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

A free body diagram (FBD) is a visual tool for identifying forces and moments acting on a selected object. Learning to isolate the object and identify its interactions is the foundation for solving problems in statics and dynamics.

A body is called free when it is singled out from other bodies for analysis. “Free” does not mean that it has no forces or is unconstrained in reality. It means that we analyze it separately so we can focus on the forces and moments acting on it.

All flashcards

What is a free body?
A body selected and separated conceptually from other bodies for analysis. It can still experience forces and moments.
What is a free body diagram?
A simplified diagram of a selected body showing the external forces and moments acting on it.
When is a particle model appropriate in mechanics?
When the body's size and rotational effects are unimportant to the analysis.
What does a support reaction represent on a free body diagram?
The force or moment exerted by a support or connection on the selected body.
What is a kinetic diagram?
A diagram showing the net force and/or moment associated with a body's motion.

Quiz questions

  1. When is a rigid extended-body model suitable for an object?Answer: When rotation matters but deformation does not.
  2. Which vectors are generally excluded from a free body diagram because they are not forces acting on the body?Answer: Velocity and acceleration vectors.
  3. Body A pushes on body B. Which interaction force belongs on a free body diagram of B?Answer: The force exerted by A on B.
  4. Which set of equations expresses two-dimensional static equilibrium?Answer: ∑Fx=0\sum F_x = 0, ∑Fy=0\sum F_y = 0, and ∑M=0\sum M = 0
  5. A ramp makes angle θ\theta with the horizontal. What is the magnitude of a block's weight component along the ramp?Answer: mgsin⁡θmg\sin\theta

Based on the Wikipedia article Free body diagram, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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