Question

In which of the following cases of motions, the distance moved and the magnitude of displacement are equal?

• A. If the car is moving on a straight road
• B. If the car is moving in a circular path
• C. The pendulum is moving to and fro
• D. The earth is revolving around the Sun

Answer 1

The correct option is A

If the car is moving on a straight road

The explanation of the correct option

In case of option A

1. Between the initial and final places, the displacement is the shortest straight-line path.
2. The distance, on the other hand, is the length of a body's actual travel from its initial to final positions.
3. The SI unit for both displacement and distance meters.
4. A reference point is required to measure both distance and displacement.
5. Both displacement and distance are measured in the same dimensions.
6. If an object moves in a straight line and in a specific direction, both distance and displacement are identical.
7. When the motion of the body is only in one particular direction, then the path covered by the body to go from an initial to the final position has to be in a straight line since motion is only in one direction.
8. Therefore, the magnitude of the displacement and distance will be the same in this case since the displacement is the length of the straight line joining the two positions.

The explanation of the incorrect option

In case of option B

1. The distance cannot be equal to the displacement in a circular motion. The displacement of the body is zero because the body started from point A and came back to its initial position A.
2. Hence, if a car is moving in a circular motion then its distance moved and the magnitude of displacement is not equal.

In case of option C

1. The pendulum is moving to and fro, then in this case displacement can be less than distance.

In case of option D

1. The earth revolving around the sun is an example of circular motion.
2. The distance cannot be equal to the displacement in a circular motion. The displacement of the body is zero because the body started from point A and came back to its initial position A.
3. Hence, if the earth is revolving around the sun then its distance moved and the magnitude of displacement is not equal.

Hence, option A is the correct answer