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Two boxes and a pulley

  • Thread starter madah12
  • Start date
  • #1
326
1

Homework Statement


http://img148.imageshack.us/img148/8686/ssslk.png [Broken]
the two boxes and the pulley have the same mass
I=.5mr^2
the system is accelerating downwards calculate the magnitude of the acceleration


Homework Equations





The Attempt at a Solution


I will call the falling one D and the higher one U

mg-Td=ma
Td=mg-ma
Tu=ma
by torque
Td-Tu=I alpha/r
Td-Tu=I a/r^2
Td-Tu=(.5mr^2) a/r^2
Td-Tu==.5ma
mg-ma-ma=.5ma
2.5a=g
a=g/2.5=3.5
what's wrong here??
in the exam I got 4 out of 5 in this question I can't see why I didnt get a full mark I revised everything
 
Last edited by a moderator:

Answers and Replies

  • #2
50
0
a=g/2.5=3.5
Try doing this part again

Remember: g=9.81m/s2
 
  • #3
326
1
uh lol so after all that work my error was numerical serves me right for using my head and not the calculator in this exam because I thought it was an easy division they should have only subtracted a half -.-
 

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