Finding F1 -- Summing forces on a box 1. The problem statement, all variables and given/known data There are two forces on the 2.80 kg box in the overhead view of the figure but only one is shown. For F1 = 10.9 N, a = 10.2 m/s2, and θ = 34.9°, find the second force (a) in unit-vector notation and as (b) a magnitude and (c) a direction. (State the direction as a negative angle measured from the +x direction.) I'm not sure if this link will work, but here's the picture: http://edugen.wileyplus.com/edugen/courses/crs7165/art/qb/qu/c05/fig05_32.gif 2. Relevant equations ∑F=ma ∑F=F1+F2...+ 3. The attempt at a solution Ok so I've been stuck on this one for a while. I started out finding the sum of the forces: ∑F=(2.8kg)(10.2m/s2)=28.56 N Then I tried solving for F2: 28.56N=10.9N+F2 F2=17.66 Then I found the x and y components of the acceleration: ax=10.2*sin(34.9)=5.84m/s2 ay=10.2*cos(34.9)=8.37m/s2 Could you multiply ax and ay by the mass and get the F1x and F1y? I'm so confused, could someone please help guide me through this problem?