I have two 1D problems:
A) A rocket that goes upwards with acceleration a, upwards, so positive, using it's engine thrust. So it has a field force:
fx1 = a*ρ (ρ:density) and nodal forces: Fb1=Fb2=A*fx1*L/2
B) A 1D bar in the x-direction that is fixed to point A (left) and goes to the right with an acelaration to the right of 10g (g=9.81 m/s^2). So it has a field force: fx2 = 10g*ρ (ρ:density) and nodal forces: Fb1=Fb2=A*fx2*L/2
Which one is the correct answer (Use d'alembert or not) :
1) fx1 = - a*ρ (negative) downwards and fx2 = 10g*ρ (positive) to the right
2) fx2 = - a*ρ (negative) downwards and fx2 = -10g*ρ (negative) to the left
3) fx1 = a*ρ (positive) upwards and fx2 = 10g*ρ (positive) to the right
4) fx1 = a*ρ (positive) upwards and fx2 = -10g*ρ (negative) to the left