Calculate elevator acceleration using mass

[aleah]

Homework Statement

A man with a mass of 65kg is traveling in an elevator and stands on a set of scales, at a given instant the scales measure his weight to be 72kg, find the acceleration of the equation

Homework Equations

f=ma
w=mg
FN =mg+ma[/B]

The Attempt at a Solution

[/B]
I know that the weight with gravity is 65kg and then changes to 72kg when he gets into the elevator because the elevator is pushing back onto him. I also know the elevator is going UP because of the positive change in weight.

Fn = 65kg + 72kg
Fn = 137kg

How do I find the acceleration?

 

[BvU]

from the last of your equations!

 

[aleah]

I did use the last equation to find that but I am not entirely sure how to get a on its own

from the last of your equations!

 

[BvU]

by the way, you should get used to writing forces in Newtons, not in kg
kg is a unit of mass

 

[aleah]

by the way, you should get used to writing forces in Newtons, not in kg
kg is a unit of mass

from the last of your equations!

do I divide the 65N by gravity to find m ? and then divide to get a on its own?

 

[BvU]

so you have fn = ma + mg and you have a scale that registers a force corresponding to m’g = 72 kg, in other words fn = ??
( the 137 you ventured is little high ...)

 

[BvU]

do I divide the 65N by gravity to find m ? and then divide to get a on its own?

yep!

 

[aleah]

thank you! I have the answer as the acceleration being 10.86ms-1

 

[BvU]

that would be a violent affair, if it would be the acceleration of the elevator alone ...

 

[BvU]

with gravity is 65kg and then changes to 72kg

that's right. So the change corresponds to the acceleration