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What is Displacement in Physics?
Grade Level:
Class 10
AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine
Definition
What is it?
Displacement is the shortest distance between an object's starting point and its ending point, along with the direction. It tells us how far an object is from where it began, in a straight line, regardless of the path it took.
Simple Example
Quick Example
Imagine you walk from your home to the neighbourhood kirana store, which is 100 meters away. If you walk directly there and then directly back home, your total distance covered is 200 meters. However, your displacement is 0 meters because you ended up exactly where you started.
Worked Example
Step-by-Step
QUESTION: A delivery rider starts from point A, travels 3 km East to point B, and then 4 km North to point C. What is the rider's displacement from point A to point C?
Step 1: Understand the path. The rider first goes East, then North. This forms a right-angled triangle.
---Step 2: Identify the starting and ending points. Starting point is A, ending point is C.
---Step 3: Recognize that displacement is the straight line connecting A and C. This line is the hypotenuse of the right-angled triangle.
---Step 4: Use the Pythagorean theorem (a^2 + b^2 = c^2) to find the length of the hypotenuse.
---Step 5: Calculate: (3 km)^2 + (4 km)^2 = c^2
---Step 6: 9 + 16 = c^2
---Step 7: 25 = c^2, so c = sqrt(25) = 5 km.
---Step 8: The displacement is 5 km. To find the direction, it would be North-East from point A (specifically, at an angle from East towards North, but for Class 10, 5 km is sufficient).
ANSWER: The rider's displacement is 5 km.
Why It Matters
Understanding displacement is crucial for engineers designing rockets for ISRO or self-driving cars. It helps in precisely tracking the position of satellites in space technology and robots in AI/ML. Knowing displacement allows scientists to predict where things will end up, which is vital in many advanced fields.
Common Mistakes
MISTAKE: Confusing displacement with distance. | CORRECTION: Distance is the total path covered, while displacement is the shortest straight line from start to end, with direction.
MISTAKE: Forgetting that displacement is a vector quantity and needs direction. | CORRECTION: Always mention the direction (e.g., 5 km East, 0 km, 10 km South-West) when stating displacement.
MISTAKE: Assuming displacement can only be positive. | CORRECTION: Displacement can be positive, negative, or zero, depending on the chosen reference direction. For example, moving 5m East could be +5m, and 5m West would be -5m.
Practice Questions
Try It Yourself
QUESTION: A student walks 20 meters East from their home to a bus stop, waits, and then walks back 5 meters West because they forgot their lunchbox. What is their final displacement from home? | ANSWER: 15 meters East
QUESTION: An ant crawls 4 cm North, then 3 cm West, and finally 4 cm South. What is the ant's total displacement from its starting point? | ANSWER: 3 cm West
QUESTION: A car travels 60 km North, then 80 km East, and then 60 km South. What is the magnitude of the car's final displacement from its starting point? | ANSWER: 80 km
MCQ
Quick Quiz
Which of the following statements about displacement is correct?
It is always equal to the distance travelled.
It only considers the total path length.
It is the shortest straight-line distance from the initial to the final position, including direction.
It can never be zero if an object has moved.
The Correct Answer Is:
C
Displacement focuses on the start and end points in a straight line, with direction. Options A, B, and D describe distance or incorrect properties of displacement.
Real World Connection
In the Real World
When you use a navigation app like Google Maps or Ola Cabs, the 'straight line distance' shown between two points is often related to displacement. For example, if you book an auto-rickshaw, the app calculates the shortest path, but the actual displacement from your pickup to drop-off is the straight line connecting those two points, which helps determine the 'as the crow flies' distance for air travel or drone deliveries.
Key Vocabulary
Key Terms
VECTOR QUANTITY: A quantity that has both magnitude (size) and direction. | SCALAR QUANTITY: A quantity that has only magnitude (size). | INITIAL POSITION: The starting point of an object. | FINAL POSITION: The ending point of an object. | MAGNITUDE: The size or numerical value of a quantity.
What's Next
What to Learn Next
Great job understanding displacement! Now that you know about displacement, you're ready to learn about 'Velocity'. Velocity builds directly on displacement, as it tells us how fast an object's displacement changes over time. Keep up the good work!
