Question 278 of 949
A person walks 4 meters east and then 3 meters north. What is the person's total displacement from the starting point?
- 5 meters
- 7 meters
- 3 meters
- 4 meters
Correct Answer:
A
Explanation
**Correct Option: A. 5 meters**
### Step-by-Step Explanation
1. **Understanding Displacement**: Displacement is a vector quantity that refers to the shortest distance from the initial position to the final position, along with the direction. It is different from distance, which is a scalar quantity that only considers the total path traveled.
2. **Visualizing the Movement**:
- The person first walks **4 meters east**. We can represent this movement on a coordinate system where east is the positive x-direction.
- Next, the person walks **3 meters north**. In our coordinate system, north is the positive y-direction.
3. **Setting Up the Coordinates**:
- Starting point (initial position) can be considered as the origin (0, 0).
- After walking 4 meters east, the new position is (4, 0).
- After walking 3 meters north from (4, 0), the final position is (4, 3).
4. **Calculating Displacement**:
- To find the displacement, we need to calculate the straight-line distance from the starting point (0, 0) to the final position (4, 3).
- We can use the Pythagorean theorem, which states that in a right triangle, the square of the hypotenuse (displacement in this case) is equal to the sum of the squares of the other two sides.
\[
\text{Displacement} = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}
\]
where \((x_1, y_1)\) is the initial position and \((x_2, y_2)\) is the final position.
Plugging in the coordinates:
\[
\text{Displacement} = \sqrt{(4 - 0)^2 + (3 - 0)^2} = \sqrt{4^2 + 3^2} = \sqrt{16 + 9} = \sqrt{25} = 5 \text{ meters}
\]
5. **Conclusion**: The total displacement from the starting point is **5 meters** in a direction that can be described as northeast, since it is a combination of east and north movements.
### Explanation of Other Options
- **Option B (7 meters)**: This option might confuse distance with displacement. The total distance traveled is 4 meters east + 3 meters north = 7 meters, but this is not the displacement, which is the straight-line distance.
- **Option C (3 meters)**: This option incorrectly assumes that the displacement is only the northward movement. Displacement considers both the east and north movements, not just one direction.
- **Option D (4 meters)**: This option only considers the eastward movement and ignores the northward component. Displacement must account for both movements.
### Common Pitfalls
- Confusing distance with displacement: Remember that distance is the total path traveled, while displacement is the shortest straight-line distance between two points.
- Forgetting to use the Pythagorean theorem when dealing with right triangles formed by movements in perpendicular directions.
### Revision Summary
- Displacement is the shortest distance from the starting point to the final position, considering direction.
- Use the Pythagorean theorem to calculate displacement when movements are in perpendicular directions.
- The correct displacement in this scenario is 5 meters, calculated from the coordinates of the starting and ending points.
- Always differentiate between total distance traveled and displacement to avoid confusion.