Theme A - Space, Time & Motion
Understanding Instantaneous & Average Speed: A Student's Journey Explained
Table of content
Hello young physicists! Today we're going to tackle two fascinating aspects of motion - instantaneous speed and average speed. These might sound complicated, but don't worry, we'll make it as simple as baking your favourite chocolate chip cookies!
Instantaneous speed
Think of it this way, you're on a bus ride and you glance at the speedometer. What you see is your bus's instantaneous speed, it's the speed your bus is going at that very instant. It's kind of like catching your bus in a candid photo!
- Instantaneous speed varies throughout a journey as the bus speeds up, slows down or navigates through traffic.
- On a distance-time graph, instantaneous speed is represented by the gradient (slope) at a specific point.
- You can calculate it by drawing a tangent to the curve at that point, and finding the gradient of that tangent.
Example: Let's say at 1000 seconds into the journey, you plot a tangent. The change in distance (y-axis) is 2000m and the change in time (x-axis) is 400s. So the gradient, or instantaneous speed, is 2000m ÷ 400s = 5.0ms−1. Like getting a snapshot of the bus's speed at that 1000 second mark!
In math terms, it's written as ds/dt, where 's' is the distance travelled and 't' is the time, and it essentially means the rate of change of position with respect to time.
Average speed
Now, you know how you'd calculate your average score in a video game? That's kind of how average speed works. It doesn't care about the highs and lows in speed during the journey, but rather the total distance covered and the total time taken.
- Average speed = Total distance travelled ÷ Total time taken for the journey.
- On a distance-time graph, average speed equals the gradient of the straight line that joins the start and end of the journey.
Example: Suppose your bus journey ends with a total distance of 800m covered in 870s, including a wait at the stop. The average speed then is 800m ÷ 870s = 0.92ms−1.
A little note to remember: All of this applies to both speed and velocity. The key difference is that velocity includes direction. It's like saying "the bus is moving at 5.0ms−1" (speed) versus "the bus is moving at 5.0ms−1 towards north" (velocity).
Keep your seatbelts fastened, because our journey in physics is just getting started. Don't worry about the speed bumps, we'll navigate through them together. Let's continue making physics a piece of cake (or a tray of cookies)! 🚌💨🍪
Theme A - Space, Time & Motion
Understanding Instantaneous & Average Speed: A Student's Journey Explained
Table of content
Hello young physicists! Today we're going to tackle two fascinating aspects of motion - instantaneous speed and average speed. These might sound complicated, but don't worry, we'll make it as simple as baking your favourite chocolate chip cookies!
Instantaneous speed
Think of it this way, you're on a bus ride and you glance at the speedometer. What you see is your bus's instantaneous speed, it's the speed your bus is going at that very instant. It's kind of like catching your bus in a candid photo!
- Instantaneous speed varies throughout a journey as the bus speeds up, slows down or navigates through traffic.
- On a distance-time graph, instantaneous speed is represented by the gradient (slope) at a specific point.
- You can calculate it by drawing a tangent to the curve at that point, and finding the gradient of that tangent.
Example: Let's say at 1000 seconds into the journey, you plot a tangent. The change in distance (y-axis) is 2000m and the change in time (x-axis) is 400s. So the gradient, or instantaneous speed, is 2000m ÷ 400s = 5.0ms−1. Like getting a snapshot of the bus's speed at that 1000 second mark!
In math terms, it's written as ds/dt, where 's' is the distance travelled and 't' is the time, and it essentially means the rate of change of position with respect to time.
Average speed
Now, you know how you'd calculate your average score in a video game? That's kind of how average speed works. It doesn't care about the highs and lows in speed during the journey, but rather the total distance covered and the total time taken.
- Average speed = Total distance travelled ÷ Total time taken for the journey.
- On a distance-time graph, average speed equals the gradient of the straight line that joins the start and end of the journey.
Example: Suppose your bus journey ends with a total distance of 800m covered in 870s, including a wait at the stop. The average speed then is 800m ÷ 870s = 0.92ms−1.
A little note to remember: All of this applies to both speed and velocity. The key difference is that velocity includes direction. It's like saying "the bus is moving at 5.0ms−1" (speed) versus "the bus is moving at 5.0ms−1 towards north" (velocity).
Keep your seatbelts fastened, because our journey in physics is just getting started. Don't worry about the speed bumps, we'll navigate through them together. Let's continue making physics a piece of cake (or a tray of cookies)! 🚌💨🍪
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