# Final velocity of the mass

1. Oct 2, 2008

### Pakbabydoll

1. The problem statement, all variables and given/known data
A spring with a spring- constant 3.4N/ cm is compressed 29cm and released. The 2 kg mass skids down the frictional incline of height 50 cm and inclined at 21 degrees angle.
The acceleration of gravity is 9.8 m/s^2.
The path is frictionless except for a distance of .07 m along the incline which has a coefficient of friction of 0.5.

2. Relevant equations
I am kind of completely lost.

3. The attempt at a solution
so far this is what I have but its probably wrong anyway

50cos(21)= 46.67902132486
50sin(21)= 17.9183974

N=mg
N= (2)(9.8)= 19.6

Friction= NmK
Friction= (19.6)(0.5)= 9.8

PE= 14.297m
KE= 9.8

Total Energy= 24.097

Problem attached its #6..
Thanks

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2. Oct 2, 2008

### Staff: Mentor

The normal force while on the incline doesn't equal mg.

What's the total energy of the mass initially?

How much energy is dissipated due to work against friction as it slides down?

What's the final energy?

3. Oct 2, 2008

### Pakbabydoll

So to get the normal force on an incline can I use the angle? Would it be like 9.8*cos(21)*2?
and how do you get friction for a specific area?

4. Oct 2, 2008

### Staff: Mentor

Yes.
Just like for anywhere else. Kinetic friction = μN.