# Work done by normal foce

1. Jan 30, 2012

### Vontox7

Hello,
I have become very confused after i tried to solve this question.
A rope pulls a 2 kg object straight up, accelerating it from rest at 2.2 m/s^2 for 3 seconds.
they want the work done by each force acting on it.
Ok i found the displacement as 9.9 m up. Then i found out that the applied force does 43.56 J and that Fn does 150.678 J and gravity does 194.238 J .

Then they ask for the total mechanical work done. I just added the works and got -.678 . Then they ask for the net force which is 4.4 N up and work done by the net force which is 43.56 J.

I am confused about finding the net work when fg,fn, fapp are involved what am doing wrong. Also when solving other questions do i include fn and fg when the displacement is vertical?

Please help and thank you. i would add more detail but i got no time to study.

2. Jan 30, 2012

### Spinnor

E initial = E final

0 = - mg*X + F*X + mV^2/2

You can figure out all three.

?

3. Jan 30, 2012

### Vontox7

I am sorry but i don't understand your formula. yes, i know that initial potential and kinetic energy equal the final but the next line i don't understand what it is nor how it can help.

4. Jan 30, 2012

### Redbelly98

Staff Emeritus
What is Fn, a normal force? Are you sure there is a normal force acting on the object while it is accelerating upward?