The provided solution is correct in terms of applying the horizontal force equilibrium condition at point C. However, it's important to understand the context and the meaning of the negative sign in the final result.Here's a breakdown:* **Horizontal Force Equilibrium:** The equation
states that the sum of all horizontal forces acting on a point must be zero for the point to be in equilibrium. This is a fundamental principle in statics.* **Applying the Principle:** You correctly applied this principle to point C, considering the internal normal force
acting to the left and the horizontal component of force
acting to the right.* **Negative Sign:** The negative sign in the result
indicates that the direction of the internal normal force
is opposite to the assumed direction. Since we initially assumed
to be acting to the left, the negative sign means it's actually acting to the **right**.**In summary:**The solution correctly applies the horizontal force equilibrium principle. The negative sign in the result for
simply indicates that the force acts in the opposite direction to what was initially assumed. To make the solution even clearer, you could explicitly state:"Therefore, the internal normal force
at point C has a magnitude of 30 kN and acts to the right."