Note that displacement has a direction as well as a magnitude. In one-dimensional motion, direction can be specified with a plus or minus sign. When you begin a problem, you should select which direction is positive usually that will be to the right or up, but you are free to select positive as being any direction.
Thus her displacement is. In this coordinate system, motion to the right is positive, whereas motion to the left is negative. His displacement is negative because his motion is toward the rear of the plane, or in the negative x direction in our coordinate system. Although displacement is described in terms of direction, distance is not.
Distance is defined to be the magnitude or size of displacement between two positions. Note that the distance between two positions is not the same as the distance traveled between them. Distance traveled is the total length of the path traveled between two positions.
Distance has no direction and, thus, no sign. For example, the distance the professor walks is 2. The distance the airplane passenger walks is 4. It is important to note that the distance traveled , however, can be greater than the magnitude of the displacement by magnitude, we mean just the size of the displacement without regard to its direction; that is, just a number with a unit.
For example, the professor could pace back and forth many times, perhaps walking a distance of m during a lecture, yet still end up only 2. In kinematics we nearly always deal with displacement and magnitude of displacement, and almost never with distance traveled.
One way to think about this is to assume you marked the start of the motion and the end of the motion. It is important to note the difference between distance traveled and displacement since, in general, they are different concepts that are often confused.
Distance traveled is a scalar magnitude that is measured over the trajectory. Displacement is a vector magnitude that depends only on the initial and final position of the body and which is independent of the trajectory. Imagine a body that moves on a circular path, thus returning to the starting point. In contrast, the displacement vector is 0 because the position vector at the beginning of the movement and the position vector at the end are the same. This example shows the trajectory that a body follows, as well as its initial and final positions.
The displacement of the cars is somewhere near 0 miles since they virtually finish where they started. Yet the successful cars have covered a distance of miles. Physics Tutorial. My Cart Subscription Selection.
Student Extras. Curriculum Corner Learning requires action. Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion. Displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.
Check Your Understanding 1. See Answer. Explanation: One can also say that displacement is a vector as we often say that we have a displacement in x - direction or alike. Hopefully, this makes the distinction clearer. Related questions How do I determine the molecular shape of a molecule? What is the lewis structure for co2?
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