Elevator acceleration formula

[snipefour]

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

 

[rock.freak667]

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?

 

[snipefour]

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