Noninertial Frames of Reference Question

[scintillate10]

Homework Statement

A mass of 2 kg lies on a horizontal table that is placed in the back of a truck. The mass is held in position by a string and a force of 6 N acts on it in the -y direction. The truck then accelerates in the +x direction. As a result, an observer in the truck sees that the string holding the mass on the table makes an angle of 20 degrees with respect to its initial orientation. What is the acceleration of the truck? Describe what the observer in the truck sees and how he might interpret his observations.

Homework Equations

http://physics-help.info/physicsguide/mechanics/noninertial_mechanics.shtml
I used this site as a guide

The Attempt at a Solution

I said m = 2 kg
F = mg sin theta - 6 N
and that is equal to 6.7 N
F_a = -m(a_o)

so then i did
m(a) = F + F_a
i got a_o = 0.35 m/s^2

but I'm not sure at all if that is right
could someone please explain this problem to me ? Thanks so much! ^.^

 

[ehild]

Try to draw the figure according to the problem. I do not understand where is that string, and how does that force act.

ehild