Acceleration/tension of two masses connected by a cord?

Question

https://i.stack.imgur.com/gl8Ou.png

For a, I did:

2.8 - 3.6sin30 * 9.8 / 3.6+2.8

= 1.5

Does that mean 1.5 is the answer for both questions on a?

For b, I have a = pos, so m2 is down? Is that right?

For c, I'm not sure which formula to use.

Answer 1

I believe you are correct on both (a) and (b). As for (c) you shouldn't need to employ any new formula. Think of the forces on $m_2$. Using Newton's Second Law: \begin{align} \sum F_2 = -m_2a = T - m_2g \end{align} with the minus sign in front of $m_2a$ because if $m_1$ accelerates to the right (i.e. positively), then $m_2$ accelerates down (i.e. negatively).

Thanks to part (a), you know the acceleration $a$, and so you can solve the equation for $T$.