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Elevator acceleration formula

  • Thread starter snipefour
  • Start date
  • #1
2
0

Homework Statement



the question given is:

What would the reading on a bathroom scale be if a 60kg pupil was accelerated upwards at a rate of 3m.s-2


Homework Equations



F=m(g-a)
F=ma

The Attempt at a Solution




F=m(g-a)
F=60kg(10m.s-2-3m.s-2)
F=600-180
F=420N which is equal to the force on the person
The reading on the scale is therefore (42kg + 60kg) or 102kg but this seems too high

Thanks for helping :wink:
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,230
31
The resultant force,F is upwards. The forces acting are the normal reaction upwards,R, and the weight W. Can you make a simple relationship between F,W and R?
 
  • #3
2
0
Thanks for the help rock but i figured it out just before i saw your post.

F=ma

F=60x3
F=180N
=extra force added to weight

therefore the total value showed on the scale is
W= 180N + 600N (the mass converted to weight)
W= 780N
M= 78kg

Thanks again for the help
 

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