SSC Selection Post 2025 PYQ — Question 5

. Correct Answer

Displacement includes direction; distance does not

Explanation

The primary difference between distance and displacement lies in their dependence on direction.

Distance is defined as the total length of the actual path traveled by an object moving from an initial position to a final position. It only measures the magnitude (numerical value) of the path covered, completely ignoring the direction of motion. Because it has magnitude but no specific direction, distance is classified as a scalar quantity. It can never be negative or zero if an object has actually moved.

Displacement, on the other hand, is defined as the shortest straight-line distance measured from the initial position to the final position of the moving object. It focuses entirely on the change in position and explicitly includes the direction pointing from the start point to the end point. Because it possesses both a magnitude and a specific direction, displacement is classified as a vector quantity. Depending on the final direction and position relative to the starting point, displacement can be positive, negative, or even zero (such as when an object travels in a complete circle and returns to its exact starting point).

Key Points

Distance can be greater than or equal to the magnitude of displacement, but it can never be less than displacement.

The SI unit for measuring both distance and displacement is the meter (m).

When a body moves along a straight line in a single direction without turning back, the magnitude of its distance covered exactly equals the magnitude of its displacement.

Important Questions and Answers

Question: An athlete runs around a circular track of radius R and completes exactly one full lap. What is the total distance covered and the net displacement of the athlete?

Answer: The total distance covered is equal to the circumference of the track (2πR), while the net displacement is zero because the final position matches the initial position.

Question: Why can displacement be a negative value while distance is always positive for a moving object?

Answer: Displacement is a vector quantity that depends on a specific directional coordinate framework, allowing negative values to indicate motion in the opposite direction. Distance is a scalar that simply accumulates total path length.