Mechanical engineeringLesson 1 of 2 in the course Dynamics

Particle and Rigid-Body Kinematics: Motion, Coordinates, and Constraints

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

Kinematics describes how objects move without asking what forces cause their motion. This lesson introduces the scope of kinematics and the tools used to describe position and trajectories.

Kinematics is the study of the geometrical aspects of motion: where objects are, how their positions change, and how their motion can be represented mathematically. It does not require knowledge of an object's mass or the forces acting on it. By contrast, dynamics studies how forces affect motion.

All flashcards

Average velocity
Displacement divided by elapsed time over an interval.
Speed
The non-negative magnitude of velocity.
Centripetal acceleration
Inward radial acceleration caused by a change in velocity direction.
Homogeneous transformation
A matrix representation that combines planar rotation and translation.
Degree of freedom
The number of independent coordinates needed to specify a system's configuration.

Quiz questions

  1. A wheel of radius rr rolls straight without slipping with angular-speed magnitude ∣ω∣|\omega|. What is the magnitude of its center's velocity?Answer: r∣ω∣r|\omega|
  2. During pure translation of a rigid body, how do the instantaneous velocities and accelerations of its points compare?Answer: Every point has the same velocity and acceleration.
  3. What motion does an ideal cylindrical joint permit between two components?Answer: Rotation and translation along the same axis.
  4. Which statement best describes a holonomic constraint?Answer: It can be expressed as a relationship among positions and time.
  5. For a point at perpendicular distance rr from a fixed rotation axis, what is its tangential acceleration?Answer: rαr\alpha, where α\alpha is angular acceleration.

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

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