Inclined plane, Calculate friction force

[TheRedDevil18]

Homework Statement

Homework Equations

Wnet = Ek

The Attempt at a Solution

1) That was fine.
2) I just want to confirm if this answer is right?, I got 12.28N. Used work energy theorem.

Sorry for double post, edited the title

 

[haruspex]

Homework Statement

Homework Equations

Wnet = Ek

The Attempt at a Solution

1) That was fine.
2) I just want to confirm if this answer is right?, I got 12.28N. Used work energy theorem.

Sorry for double post, edited the title

Seems a bit high. Pls post your working.

 

[TheRedDevil18]

Seems a bit high. Pls post your working.

Sorry my mistake, forgot something in my calculation. Anyway heres my working

Wnet = Ek
Wg + Wf + Wn = 1/2*m(vf^2 - vi^2)
(5*9.8*sin30*20) - 20Ff + 0 = 1/2*5(12^2 - 6^2)...That 20 is the length of the incline
Ff = 11N.........Now correct?

 

[haruspex]

Sorry my mistake, forgot something in my calculation. Anyway heres my working

Wnet = Ek
Wg + Wf + Wn = 1/2*m(vf^2 - vi^2)
(5*9.8*sin30*20) - 20Ff + 0 = 1/2*5(12^2 - 6^2)...That 20 is the length of the incline
Ff = 11N.........Now correct?

Yes, that looks right.