Kinematics Question. Incline, Spring, Friction

Homework Statement

Practice problem for midterm.

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T_1+U_1=T_2+U_2
U_spring=1/2kx^2

The Attempt at a Solution

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Set X-axis along the 30 degree line and the Y-axis perpendicular.

I'm not sure how to consider the friction constant into the formula.

Any help is very much appreciated.

Answers and Replies

Simon Bridge
Science Advisor
Homework Helper
hint: work against friction.

gneill
Mentor
Calculate the friction forces (static and kinetic). Make sure the block can move when released (static friction). If the block moves against friction (kinetic friction), what work is done? What happens to the energy involved in friction?

sumF_y=0
N-mgcos30=0
N=17 N

sumF_x=0
F_spring-F_friction=m_block*accel_block
kx-uN=ma

if static, accel=0

410(0.5)-u(17)=0
u=12.06

doesnt seem right... i think the x is wrong for the spring but i can't visualize it.

gneill
Mentor
You want to compare the spring force with the static friction force. What must the relationship be if the block is to be able to move from rest?