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Kinematics

10 Time, Velocity, and Speed

Learning Objectives

  • Explain the relationships between instantaneous velocity, average velocity, instantaneous speed, average speed, displacement, and time.
  • Calculate velocity and speed given initial position, initial time, final position, and final time.
  • Derive a graph of velocity vs. time given a graph of position vs. time.
  • Interpret a graph of velocity vs. time.

 

Snails leaving slime trails as they race each other along a flat surface.
Figure 9.1: The motion of these racing snails can be described by their speeds and their velocities. (credit: tobitasflickr, Flickr)

There is more to motion than distance and displacement. Questions such as, “How long does a foot race take?” and “What was the runner’s speed?” cannot be answered without an understanding of other concepts. In this section we add definitions of time, velocity, and speed to expand our description of motion.

Glossary

average speed
distance traveled divided by time during which motion occurs
average velocity
displacement divided by time over which displacement occurs
instantaneous velocity
velocity at a specific instant, or the average velocity over an infinitesimal time interval
instantaneous speed
magnitude of the instantaneous velocity
time
change, or the interval over which change occurs
model
simplified description that contains only those elements necessary to describe the physics of a physical situation
elapsed time
the difference between the ending time and beginning time

License

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College Physics 1 Copyright © 2012 by OSCRiceUniversity is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.