# Homework Help: Finding the mass of an object

1. Sep 27, 2015

### astrololo

1. The problem statement, all variables and given/known data
An octagon is on a table with no friction. There are two equal forces which are put on two faces of the octagon, one in direction of the north, the other in direction of the south-east. These forces are all 0,5 N. If the module of the acceleration is 0,3 m/s^2, what is the mass of the object.

2. Relevant equations
Sum of Force of y = m * a in y

Sum of Force of x = m a in x

3. The attempt at a solution
I know that I must decompose my south-east forces and find its component. What I don't understand is how to find the components of the acceleration to be able to do my calculations. Could somebody give me a hint ?

2. Sep 27, 2015

### andrewkirk

You don't need to decompose the acceleration. You need to find the magnitude of the Force vector that is the vector sum of the two applied forces. Then you can use that and the given magnitude of acceleration to find the mass.

3. Sep 27, 2015

### astrololo

Oh ok, I'll try it and see what it gives.