Is the Conservation of Energy Solution Correct?

[Ammar w]

Homework Statement

Here's the problem :

http://www.diigo.com/item/image/2sb3i/wonu

Homework Equations

Ei = Ef

The Attempt at a Solution

The surface between A and B is frictionless :
Ei = Ef
K_A + U_A = K_B + U_B
mgh_A = 1/2 mv_B²
v_B² = 2gh_A = 2*9.8*3 = 58.8 m/s

The surface from C to the spring is frictionless :
Ei = Ef
1/2 mv_C² = 1/2 kx²
v_C² = kx²/m = 2250*0.32/10 = 20.25 m/s

The surface between B and C has a friction :
Ef - Ei = -f_kd
1/2 mv_C² - 1/2 mv_B² = -u_kmgd
1/2 m (v_C² - v_B²) = -u_kmgd
1/2 * 10 (20.25 - 58.8) = -u_k*10*9.8*6
u_k = 0.327

Right?

 

[VantagePoint72]

I haven't double checked each computation, but your method is correct and the final answer is reasonable.

 

[Ammar w]

LastOneStanding, Thank you.