# Homework Help: Frictionless inclined plane problem

1. Oct 15, 2012

### Chester8990

1. The problem statement, all variables and given/known data

A 2.5 kg block is placed on a movable 40° ramp weighing 120 N. The friction
coefficients between the ramp and the block are μk = 0.15 and μs = 0.35. With what
force does the ramp need to be pushed to keep the block

a) sliding at a constant speed up the ramp

b) sliding at a constant speed down the ramp

c) what range of forces keeps the block stationary on the ramp

2. Relevant equations

The only equations i can think of is F=ma, Ff= μk*mg

3. The attempt at a solution
I tried resolving the forces into components parallel to the acceleration's direction,
so for a general free body diagram of all the situations

ƩFa=ma= Fgxcos(40)+Ffcos(40)

ƩFy=ma*sin(40)=N-Fgy

Where signs can be changed according to actual situation

That's where i got stuck, I actually have the solution to this problem, but i didn't understand how the answer came about. Can anybody please offer some help? If you want i can also put the solution here
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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