Which Average Velocity Formula Should I Use?

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Homework Help Overview

The discussion revolves around the calculation of average velocity in physics, specifically comparing two different equations: (Vf + Vi)/2 and (Xf - Xi)/Δt. Participants are exploring the contexts in which each equation is applicable and the implications of using them.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the differences between the two equations for average velocity and under what conditions each should be used. There is an exploration of the assumptions related to constant acceleration and the general definition of average velocity.

Discussion Status

Some participants have provided clarifications regarding the applicability of each equation, noting that one is specific to constant acceleration while the other is a general definition. However, there is still some confusion about when to apply each formula in various problem contexts.

Contextual Notes

There appears to be a lack of consensus on the specific scenarios in which each equation is most useful, and participants are navigating through their understanding of average velocity in relation to the information given in problems.

fightboy
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Hey guys I just had a question regarding the equation to calculate average velocity. The first equation I've seen is: Vf+Vi/2, with Vf representing final velocity and Vi representing initial velocity. The second equation I've seen is Xf-Xi/Δt, with X representing position and Δt representing the elapsed time. What is the difference between the two? I get confused on which equation to use for a problem asking for average velocity.
 
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The first equation, (Vf + Vi)/2, gives the average velocity when the acceleration is constant. It's not true in general.

The second, (Xf - Xi)/Δt, is the definition of average velocity and is always true. Whether it's useful or not depends on what you are given in the problem.
 
fightboy said:
Hey guys I just had a question regarding the equation to calculate average velocity. The first equation I've seen is: Vf+Vi/2, with Vf representing final velocity and Vi representing initial velocity. The second equation I've seen is Xf-Xi/Δt, with X representing position and Δt representing the elapsed time. What is the difference between the two? I get confused on which equation to use for a problem asking for average velocity.
Notice the parentheses Doc Al added in his reply to you.
 
ok that cleared it up, thanks!
 

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