Find the direction of acceleration

Join the discussion
Registration is free. Ask a follow-up in this thread, or start your own.
4 replies · 2K views
Mustachio
Messages
9
Reaction score
0

Homework Statement



A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.66 of the person's regular weight. Calculate the acceleration of the elevator, and find the direction of acceleration.

Homework Equations



So I know you have to use sumF = MA to solve this problem.

The Attempt at a Solution



I drew a freebody diagram.
^
|
| Fn
.
|
| .66mg
V

And I got the formula N - .66mg = .66ma. This where I get stuck. I don't know what to do next.

As for the second part of the question, I know that the elevator is moving downward because of the decrease in mass.
 
Physics news on Phys.org


The normal force is 0.66mg and the person's weight is mg.
 


So I took that into account and got

.66mg - mg = .66ma
-.44 = .66ma
-.66 = ma.

Now I don't know what to do with the m. :\
 


The mass is considered to still be m on the right side of the equation. Also, 0.66mg - mg = -0.34mg.
 


Thank you. I feel very stupid right now for not noticing that arithmetical mistake.