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gap0063

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## Homework Statement

A spring with a spring-constant 2.5 N/cm is compressed 35 cm and released. The 4 kg mass skids down the frictional incline of height 37 cm and inclined at a 20◦ angle. The acceleration of gravity is 9.8 m/s

^{2}. The path is frictionless except for a distance of 0.5 m along the incline which has a coefficient of friction of 0.3.

What is the final velocity vf of the mass?

Answer in units of m/s.

k=2.5 N/cm= 250 N/m

d=35 cm=.35m

m= 4 kg

h=37cm=.37,

theta=20◦

distance of friction = .5 m

Coefficient of friction=.3

## Homework Equations

W

_{nc}=[tex]\Delta[/tex]K+[tex]\Delta[/tex]U

_{spring}+[tex]\Delta[/tex]U

_{gravity}

## The Attempt at a Solution

v

_{i}=0

so W

_{nc}=K

_{f}+ [tex]\Delta[/tex]U

_{spring}+[tex]\Delta[/tex]U

_{gravity}

W

_{nc}= 1/2mv

_{f}+ 1/2kx

^{2}+mgh

my question is... where does friction come in... f=uN=u*mg from the equation above... and which x do I use for [tex]\Delta[/tex]U

_{spring}... is it .35m? the compression of the spring?