Question regarding Newton's laws

[r3dxP]

well, my question isn't directly towards Newton's law or anythiing, but its a question on how to solve problems using Newton's law.
for example, look at this problem below..

a force of 20N acts horizontally on a mass of 10kg being pushed up a fritionless incline that makes a 30degrees angle with the horizontal. What is the magnitude of the acceleration of the mass up the incline equal to?

ok, for this problem, how would you know you solve this problem by using the equilibrium in respect to the x ? is it because only x equilibrium exists? or is it because its asking for the magnitude of the acceleration up the incline?
sorry if this question confuses you..

 

[FredGarvin]

You're going to need Newton's second law, not the first. The acceleration is what you are looking for. That's what the question states to find. Always start with what is given to and asked of you. I always put my coordinate system with the x-axis parallel to the incline. That way the only term that should need being broken down into components is the weight vector. It will have a component in both x and y directions. Write out your 2nd law equations for both axes.

 

[HallsofIvy]

This was also posted in the homework forum. Please don't double post. If this is homework it shouldn't be here. (And if it's not homework, it shouldn't be there!)