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EduAid, the first edtech company of NE India, has brought a series of live classes conducted on YouTube. These classes are meant to be beneficial for students of 9 and 10 of both CBSE and state boards. In one of such recent live classes, Bijoy Sir broke down the entire chapter of motion for Class 9. If you have by any chance missed the class, you can still view the recorded live class on YouTube. Below is the link to the class. Go and watch to clear your concept for the topic: Motion (chapter 8, science).
The Starting Point: What is Motion?
As Bijoy Sir kicked things off, he defined motion simply as the change of position of an object with respect to time. Whether it’s a car on the road or a dog running, if its position is different now than it was a moment ago, it’s in motion.
Distance vs. Displacement: The Path and the Gap
One of the most interactive parts of the class involved distinguishing between how far you walk and where you actually land.
- Distance (Path Length): This is the total length of the path an object travels.
- Displacement: This is the minimum distance between the final and initial points.
To calculate displacement, you subtract the initial position from the final position (xf–xi)..
An important rule Bijoy Sir highlighted is that while path length is always greater than or equal to displacement, displacement can actually be zero if you return to your starting point. For example, if you walk 4 km to a market and then 4 km back, your distance is 8 km, but your displacement is 0.
Scalars and Vectors: Does Direction Matter?
The class also cleared up the confusion between scalar and vector quantities:
- Scalar Quantities: These only have magnitude (a numerical value). Examples include mass, time, and distance.
- Vector Quantities: These have both magnitude and direction. Displacement, velocity, and acceleration are all vectors because where you are going matters just as much as how far you’ve gone.
Speed, Velocity, and Uniform Motion
Bijoy Sir explained that speed is the distance traveled by an object divided by time. However, when you measure distance in a proper direction, you are talking about velocity, which is displacement divided by time.
We also looked at how objects move over time:
- Uniform Motion: This happens when an object travels the same distance in equal intervals of time.
- Equations of Motion: To solve more complex problems, we use standard formulas like v=u+at, s=ut+12at2 and v2=u2+2as
The session was a deep dive into these concepts to ensure everyone, whether from CBSE or state boards, had a solid conceptual grasp before the next class.
Final Words
Value Addition | An Analogy to Help it Stick: Think of Distance like the “pedometer” on your wrist—it counts every single step you take, no matter how many circles you walk in. Displacement, however, is like a “straight-line bridge” built between where you started your day and where you ended it. The pedometer tracks your effort, but the bridge only measures the final gap.
(A pedometer is a portable device, often small and clip-on, that counts your steps as you walk or move, helping you track physical activity, distance, and calories burned)
