Simple Physics (unit analysis)

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Homework Help Overview

The problem involves unit analysis of various equations related to distance, time, and speed. Participants are tasked with identifying which equations are dimensionally inconsistent based on the provided variables.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants attempt to analyze each equation by comparing the units on both sides. Some express uncertainty about the dimensional analysis process and seek clarification on specific terms.

Discussion Status

There is ongoing exploration of the equations, with some participants providing their reasoning and questioning the validity of certain equations based on unit consistency. Guidance has been offered regarding the need to ensure that terms in equations share the same units.

Contextual Notes

Participants note the importance of using standard units, such as meters for distance and meters per second for velocity, while also expressing confusion about the dimensional analysis process.

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Homework Statement



1. (5 points)
If d is a distance, t is a time, and v is a speed, which of the following equations do unit analysis show must be wrong?

A. d = vt
B. v = 3 d^2 / t
C. t = d/v
D. v = d/t + 2 t/d
E. v = d^2 / t^2


I haven't done this since high school and have no idea. It's pretty easy, but I don't remember this at all. Any help would be greatly appreciated, thanks guys!
 
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Here's an effort of what I think its asking for..

A. d = vt
KM = KM/s(s) KM =/= KM^2 [WRONG]

B. v = 3 d^2 / t
KM/s^2 = 3KM^2 / sec KM/s^2 =/= km^2/s [WRONG]

C. t = d/v
sec = KM / KM/s^2 sec =/= s^2 [WRONG]

D. v = d/t + 2 t/d
KM/s^2 = KM/s + 2s/KM ?

E. v = d^2 / t^2
KM/s^2 = KM^2 / s^2 ?


idk.. >.<
 
Velocity is in m/s not m/s^2 or km if you want though meters is the standard.
 
Afide said:
Here's an effort of what I think its asking for..
D. v = d/t + 2 t/d
KM/s^2 = KM/s + 2s/KM ?

E. v = d^2 / t^2
KM/s^2 = KM^2 / s^2 ?

In addition to distance usually being in meters (m) and the unit for velocity being distance/time (m/s) as Chunkysalsa pointed out,

For (D); do those two terms have the same units? If so, you're golden. If not, you have a problem.

For (E) you've done the dimensional analysis correctly, so ask yourself if the right hand side is in units of distance/time.
 

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