Work, Velocity, Friction, and Potential Engery with a sliding block

[Phoenixtears]

(Green means correct)

Homework Statement

In the figure below, a small block is sent through point A with a speed of 8.1 m/s. Its path is without friction until it reaches the section of length L = 12 m, where the coefficient of kinetic friction is 0.70. The indicated heights are h1 = 8.0 m and h2 = 1.1 m.
(Image Attached)

(a) What is the speed of the block at point B?
15 m/s
(b) What is the speed of the block at point C?
14.1 m/s
(c) Does the block reach point D?
---Select--- yes no
If so, what is its speed there and if not, how far through the section of friction does it travel?
in units of m/s

Homework Equations

Kinematics equations
Mu*N= Fkinetic

The Attempt at a Solution

Now, I've already finished a, b, c, I just need help with d. I first determined that all I had to do was set up a kinematics graph and use point C as my starting point. So, my inital velocity would be 14.1, my acceleration (which I got from using the second equation above, the normal force is equal to the weight for mg) is -6.86, and my delta-x is 12.

I realize that the picture does not depict L to be 12 exactly, but I see no other way to do this. Then, using the Vf^2=Vo^2 +2ax equation I solved for Vf. My answer was 5.84 m/s, however, this is incorrect. Could someone lead me to the right direction?

Thanks in advance!

~Phoenix

 

[Doc Al]

Then, using the Vf^2=Vo^2 +2ax equation I solved for Vf. My answer was 5.84 m/s, however, this is incorrect.

Looks good to me.

(Perhaps it's a fluke in the online system. Try redoing your calculations without rounding off until the last step.)

 

[Phoenixtears]

Thanks for your response! At least I feel like I know what I'm doing... I'll redo it right now.

 

[Phoenixtears]

Hmm... turns out I didn't round anything off until the end. And still got the same answer. Perhaps I should merely confront my teacher tomorrow about the incident. Is there anything else I could possibly be doing wrong?