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Basic algebra is not working

  • Thread starter vysero
  • Start date
  • #1
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Ok so here is my problem:

Vf=Vi+at

I want to solve for t so:

(Vf-Vi)/a = t

right so now my problem starts how can this happen:

t = -Vf/a ??????

The solution above comes from this site http://www.monmsci.net/~fasano/phys1/Chapter_2_10.pdf

scroll down to problem 2.31 and you will find what I am looking at, in this situation Vi = 0 so they disregarded it and somehow during that process (at least i believe it was during that process) they came up with:

t = -Vf/a

Please explain to me how that works, where the heck did the - sign come from??
 

Answers and Replies

  • #2
11,261
4,728
looks like a typo to me. sometimes in gravity problems +v means its going up vs -v means its falling but thats not the case. notice in the actual answer the - is gone.
 
  • #3
132
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Oh well I didn't even see that lol well thank you it prob. was just a typo
 

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