posted by Anonymous .
A m = 1.85 kg box rests on a plank that is inclined at an angle of θ = 65.5° above the horizontal. The upper end of the box is attached to a spring with a force constant of 21.0 N/m. If the maximum force of static friction between the box and the plank is 1.60 N, what is the maximum amount the spring can be stretched and the box remain at rest?
weight down plank: mg*SinTheta
friction down: 1.6 (spring pulls up, friction opposes that)
spring pull-frictiondown=weight down plank
solve for x