Support reactions: For a frame or beam resting on which type of support will the reaction always be normal (perpendicular) to the plane of the support?

Introduction / Context:Choosing correct boundary conditions is essential in structural analysis. Different supports impose different reaction directions and constraints, changing internal forces and deflections.

Given Data / Assumptions:

• Idealized supports are used (roller, pin, fixed).
• Plane of the support surface is well-defined.
• No friction is assumed for the roller (classical idealization).

Concept / Approach:A frictionless roller can only transmit a force normal to its contact surface. Therefore, the reaction is always perpendicular to the plane of the support. Hinges can resist forces in two orthogonal in-plane directions; fixed supports can also resist moments.

Step-by-Step Solution:Identify role of a roller: allows translation along the plane; resists motion normal to the plane.Hence the reaction must be normal to that plane.Therefore, select “Roller support.”

Verification / Alternative check:Free-body diagrams for beams on rollers show a single reaction line perpendicular to the surface at the contact point.

Why Other Options Are Wrong:Hinged: reaction components act in predefined axes, not necessarily normal to a plane surface.Fixed: also develops moment; direction is not constrained to be normal to a plane.Free: no support reaction by definition.Cable: provides axial tension along the cable, not normal to a plane.

Common Pitfalls:Assuming friction at the roller, which would add tangential reaction; the ideal roller is frictionless.

Final Answer:Roller support.