• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Find the direction of acceleration

  • Thread starter Mustachio
  • Start date
1. The problem statement, all variables and given/known data

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.


2. Relevant equations

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

3. 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.
 
Re: Elevators

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

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. :\
 
Re: Elevators

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

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

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top