What is distance and displacement? This article focuses on this question and provides a detailed and informative answer. Read this concept explainer to understand the definition, formula, meaning, units, and calculations of displacement and distance.
Difference between distance and displacement: Humans generally not aware of the difference between distance and displacement and thus use these terms interchangeably. But scientifically, these terms have different meanings and explanations. Here, we will dive deeper into these two terms and bring out the differences between them. Science students can use this concept explainer to clarify their confusion about distance and displacement.
What is Distance?
The definition of distance is simple and easy to remember. It is the scalar quantity that measures the length of the path travelled by an object or a person. This accounts for the entire journey, including any curves or deviations. For example, if you walk around a park and return to your starting point, the distance covered is the sum of the lengths of all the paths you walked. Distance is always positive and is measured in various units.
Let us understand this with an illustration. The image below shows a boy walking around the triangular park and we have to calculate the total distance covered by him in one complete round from the point A to B to C and again back to A.
Total distance travelled = Distance from Point A to B + Distance from Point B to C + Distance from Point C to A
Total distance travelled = 5m + 8m + 5m = 18m
Distance Formula
Based on the above example we can easily deduce the distance formula. It would be:
Change in the position (Δd)=Length of Path Covered (d)
Add the path length if covered in pieces or intervals then the formula would be:
- Δd= d1 + d2
Distance in physics is also defined as the product of time spent and the speed of the object to cover a defined path.
- Distance = Speed x Time
Thus, distance is directly dependent on time and speed.
Unit of Distance
The unit of distance is typically measured in units of length. The most commonly used units of distance include:
- metres (m): The base unit of length in the International System of Units (SI).
- Kilometres (km): Equal to 1,000 metres, commonly used for measuring longer distances such as travel between cities.
- Centimetres (cm): Equal to one-hundredth of a metre, often used for shorter lengths and small objects.
- Millimetres (mm): Equal to one-thousandth of a metre, used for very small distances and precision measurements.
- Miles (mi): Used primarily in the United States and the United Kingdom for measuring long distances, equal to 1.609 kilometres.
- Feet (ft): Commonly used in the United States for various measurements, equal to 0.3048 metres.
- Inches (in): Also used in the United States for smaller measurements, equal to 2.54 centimetres.
Other units, such as yards and nautical miles, are also used in specific contexts. The choice of units depends on the region and the size of the area we aim to measure.
What is Displacement?
Displacement is a vector quantity that measures the shortest path or length between the initial and the final positions of an object considering the direction of the motion. This vector quantity has both, magnitude and direction.
For example, if you walk 3 kilometres east and then 4 kilometres north, your total distance travelled is 7 kilometres, but your displacement is 5 kilometres in a northeast direction, as calculated using the Pythagorean theorem.
Displacement Formula
Displacement is simply calculated using a basic formula that students study while going through this topic. The formula for displacement is:
Change in Position (ΔX) = Final Position (Xf)- Initial Position (X0)
Units of Displacement
The units of displacement are the same as the units of distance since both measure lengths. Common units of displacement include:
- Metres (m)
- Kilometres (km)
- Centimetres (cm)
- Millimetres (mm)
- Miles (mi)
- Feet (ft)
- Inches (in)
Difference Between Distance and Displacement
This table summarises the key differences between distance and displacement:
| Feature | Distance | Displacement |
| Definition | The total length of the path travelled by an object. | The shortest straight-line path between the object's starting and ending positions. |
| Direction | Does not consider direction (Scalar Quantity) | Considers direction (Vector Quantity) |
| Value | Can be zero or any positive value. | Can be positive, negative, or zero. (Zero if the object returns to its starting point) |
| Dependence on Path | Depends on the actual path taken. | Independent of the path taken, only considers starting and ending points. |
Distance and Displacement Simple Calculations
Calculation 1: Distance
Scenario:A car travels along a straight road from point A to point B and then returns to point A.
- Given:
- Distance from point A to point B = 40 kilometres
- Calculation:
- Total distance travelled = Distance to point B + Distance from point B back to point A
- Total distance travelled = 40 km + 40 km
- Total distance travelled = 80 kilometres
- Result:
- The total distance travelled by car is 80 kilometres.
Calculation 2: Displacement
Scenario:A bicycle starts at point A and moves to point B, where:
- Initial position (X₀) = 10 metres
- Final position (Xf) = 40 metres
Given:
- Change in position (ΔX) = Final position (Xf) - Initial position (X₀)
Calculation:
- ΔX = Xf- X₀
- ΔX = 40 m - 10 m
- ΔX = 30 metres
Result:
- The displacement of the bicycle from point A to point B is 30 metres.
References and Further Reading
- Books
NCERT Class 10 Science Textbook PDF
NCERT Class 12 Physics Textbook PDF
- Articles
Magnetic effects of Electric Current
- Online Resources
CBSE Class 10 Science Video Tutorials
CBSE Class 12 Physics Video Tutorials
Also Check:
- CBSE Class 10 Science Syllabus 2024-25: Download PDF
- CBSE Class 12 Syllabus 2024-25 PDF (All Subjects)
- CBSE Class 11 Syllabus 2024-25: Latest and Revised PDF
