A roller support has how many reactions?

A roller support has how many reactions?

• A. None
• B. 1
• C. 2
• D. 3

Answer: (B)

A roller support provides a single reaction force, directed normal to the contact surface. It resists motion perpendicular to that surface while allowing sliding along it, so there is only one independent reaction component (for a horizontal surface this is a vertical reaction). In contrast, a pin would give two reactions (horizontal and vertical) and a fixed support would add a moment, totaling three in 2D.

A roller support provides a single reaction force, directed normal to the contact surface. It resists motion perpendicular to that surface while allowing sliding along it, so there is only one independent reaction component (for a horizontal surface this is a vertical reaction). In contrast, a pin would give two reactions (horizontal and vertical) and a fixed support would add a moment, totaling three in 2D.