Final answer:
The notation QR with a left-right arrow on top designates QR as a vector, which is a quantity having both magnitude and direction The correct option is c) Vector
Step-by-step explanation:
The notation QR with a left-right arrow on top indicates that QR is a vector. In physics and mathematics, vectors are used to represent quantities that have both magnitude and direction, distinguishing them from scalars, which only have magnitude. When depicted in diagrams, vectors are often shown as arrows, with the length of the arrow representing the magnitude and the direction of the arrow indicating the direction of the vector.
In the context of a free-body diagram, which is used in physics to illustrate the forces acting upon an object, vectors are essential. They represent forces with arrows, where the length of the arrow is proportional to the force's magnitude and the arrow points in the direction of the force's application. For example, a dot with an arrow labeled F, pointing right, represents a force vector in that particular direction.
The term ray in mathematics refers to a straight line that originates from a point and extends infinitely in one direction. Although rays share the concept of having a direction with vectors, rays do not have a magnitude and are thus a different form of mathematical notation. While both vectors and rays can be represented using arrows, a vector also incorporates magnitude and is used specifically in the context where direction and size (magnitude) are both relevant. Hence, the symbol QR with an arrow on top signifies a vector rather than a ray, line segment, or line.