What kind of quantity is displacement

Some physical quantities, like distance, either have no direction or none is specified. A scalar is any quantity that has a magnitude, but no direction. In this case, the minus sign indicates a point on a scale rather than a direction. Scalars are never represented by arrows.

In order to describe the direction of a vector quantity, you must designate a coordinate system within the reference frame. For one-dimensional motion, this is a simple coordinate system consisting of a one-dimensional coordinate line. In general, when describing horizontal motion, motion to the right is usually considered positive, and motion to the left is considered negative.

With vertical motion, motion up is usually positive and motion down is negative. In some cases, however, as with the jet in Figure 1, it can be more convenient to switch the positive and negative directions. For example, if you are analyzing the motion of falling objects, it can be useful to define downwards as the positive direction. If people in a race are running to the left, it is useful to define left as the positive direction.

It does not matter as long as the system is clear and consistent. Once you assign a positive direction and start solving a problem, you cannot change it. Figure 2. Distance and Displacement Distance is a scalar quantity. Example A girl walks 3 km due north then turns and walks 4 km due east as shown in the diagram. Speed and Velocity Speed is a scalar quantity.

Since velocity is a vector, you must state its direction. The direction of velocity will be the same as the displacement. Leave a Reply Cancel reply Your email address will not be published. Cookie policy Privacy policy. Scalar quantities include:. Scalar quantities change when their magnitude changes. Vector quantities have both magnitude and direction. Vector qualities include:.

Vector quantities change when:. The difference between scalar and vector quantities is an important one.