Fun with FISIX!

[GoldenBear]

I'm kind of sick and all, and my mind isn't working at all right now, so anyone with a little sympathy and a working brain care to help?

A person stands on a bathroom scale in a motionless elevator. When the elevator begins to move, the scale briefly reads only 0.75 of the person's regular weight. Calculate the acceleration of the elevator and find the direction of acceleration....

 

[Angrymarshmello]

I dropped out of Physics last semester and I recall we had a problem exactly like this....

If I recall you need to use the G=9.8 m/s^2 thing and somehow figure something out... (I'd help you out but I didn't pass Physics so I really can't)

 

[yakko]

<< Calculate the acceleration of the elevator and find the direction of acceleration.... >>

No.

 

[Thanatopsis]

I can tell you the elevator moved down, but that's about it

 

[Thanatopsis]

This problem could it pretty complicated if its one of those diagonal elevators they have in the Luxor hotel @ Las Vegas

 

[RichieZ]

damn it all, i can't even remember stuff that was on our first test!

 

[poop]

Actually, you cannot find the direction of the acceleration, other than it is someway goig towardes the earth. If you were moving diagonally, then the Y component is going to be the same as if you were moving down with the same Y acceleration.

Otherwise, I would help you, but this questions is REALLY easy. Just think about it for a second...

On second thought, here is a hint:
F=ma
.75F=.75ma

Any other help, and I would be telling you the answer.

EDIT:
Richie's answer is wrong. Richie, I hope your AP teacher is not here. Think about it. If the elevator begins to accelerate at over 13 m/ss, then you will hit the ceiling when the floor leaves your feet. If the elevator is goign faster than freefall, then it is acutally goign to be pusing you to the earth, not allowing you to feel any effects of gravity. You need to think about NET acceleration. You will be feeling NET .75*g. So the elevator is moving down at .25*g.

 

[RichieZ]

damn you FIZIX! (thats the preferred way of spelling it at my school )

 

[GoldenGuppy]

The answer goes like this..

Fg (force of gravity ) = mg where g is -9.8

so he says 0.75 of the weight

So it'd be .75 of the force also...

So you have -9.8m (m = mass which is just a variable in this case) ... -9.8m=0.75(-9.8)m +ae (acceleration of the elevator) m ...

All the m's cancel out leaving you w/ -9.8=7.35+ae which equals roughly -


-2.5 m/s^2