Hi everyone, my first of what I can only imagine will be many questions here.(adsbygoogle = window.adsbygoogle || []).push({});

I’ve been learning some kinematic equations and have been doing pretty well calculating acceleration. The issue I’m having is this. I found this tutorial http://www.dummies.com/education/sc...-and-distance-from-acceleration-and-velocity/ on calculating time and distance from acceleration and velocity:

Imagine you’re a drag racer. Your acceleration is 26.6 meters per second2, and your final speed is 146.3 meters per second. Now find the total distance traveled.

You know the acceleration and the final speed, and you want to know the total distance required to get to that speed. This problem looks like a puzzler, but if you need the time, you can always solve for it. You know the final speed, vf, and the initial speed, vi (which is zero), and you know the acceleration, a. Because vf – vi = at, you know that:

t = vf - vi / a

t = 146.3m/s - 0m/s / 26.6m/s2

t = 5.5s

Now you have the time. You still need the distance, and you can get it this way:

s = vit + 1/2at2

The second term drops out because vi = 0, so all you have to do is plug in the numbers:

s = 1/2at2

s = 1/2(26.6m/s2)(5.5s)

s = 402m

In other words, the total distance traveled is 402 meters

I managed to follow along without a problem. I changed some numbers around and managed to recreate the process without looking at the tutorial. Then I began to wonder if it would be possible to calculate velocity given just distance and time (this may or may not have come up when talking comic books with a friend lol). I tried doing it using the numbers provided in the example but I always end up with a different number and it’s always exactly half and I can’t seem to understand why.

Let’s use the same numbers

Distance = 402m

Time = 5.5s

If I want to calculate the average velocity I believe (correct me if I’m wrong please) it is:

v = d/t

So:

v = 402/5.5

v = 73m/s (half of what was given in the example)

I can’t seem to understand what I am doing wrong. Any help would be greatly appreciated thank you.

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# B How to calculate velocity based on distance and time?

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