78 lines
2.7 KiB
Markdown
78 lines
2.7 KiB
Markdown
# Acceleration
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Get the acceleration value (milli g-force) in one of three dimensions, or the combined force in all directions (x, y, and z).
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Find the acceleration of the @boardname@ (how fast it is speeding up or slowing down).
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```sig
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input.acceleration(Dimension.X);
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```
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## ~hint
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You measure acceleration with the **milli-g**, which is 1/1000 of a **g**.
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A **g** is as much acceleration as you get from Earth's gravity.
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## ~
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Watch this video to learn how the accelerometer on the @boardname@ works:
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https://www.youtube.com/watch?v=byngcwjO51U
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## Parameters
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* **dimension**: the direction you are checking for acceleration, or the total strength of force.
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>`x`: acceleration in the left and right direction.<br/>
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`y`: acceleration in the forward and backward direction.<br/>
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`z`: acceleration in the up and down direction.<br/>
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`strength`: the resulting strength of acceleration from all three dimensions (directions).
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### ~hint
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**Forces in space**
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Since we don't live on a flat world, forces happen in three dimensional space. If the movement of an object isn't exactly in the direction of one axis, we need a way to calculate its acceleration from the values measured for all the axes together.
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If you put your @boardname@ on a level table and push it diagonally, you have an acceleration in two dimensions. You can find the acceleration in that direction just like how you calculate the long side of a triangle using the two shorter sides (**X** and **Y**):
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```strength2D = Math.sqrt((accelX * accelX) + (accelY * accelY))```
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If you decide to lift your @boardname@ off the table, then you've just added another dimension, so insert the acceleration value for the **Z** axis into the equation:
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```strength3D = Math.sqrt((accelX * accelX) + (accelY * accelY) + (accelZ * accelZ))```
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This calculation is called the [Euclidean norm](https://en.wikipedia.org/wiki/Euclidean_norm) of acceleration.
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### ~
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## Returns
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* a [number](/types/number) that means the amount of acceleration. When the @boardname@ is lying flat on a surface with the screen pointing up, `x` is `0`, `y` is `0`, `z` is `-1023`, and `strength` is `1023`.
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## Example: bar chart
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This example shows the acceleration of the @boardname@ with a bar graph.
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```blocks
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basic.forever(() => {
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led.plotBarGraph(input.acceleration(Dimension.X), 1023)
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})
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```
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### Example: quake meter
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Every 5 seconds, with the @boardname@ facing upward on a flat surface, show how much the earth is shaking (if at all).
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```blocks
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basic.forever(() => {
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basic.showNumber(input.acceleration(Dimension.Strength))
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basic.pause(5000)
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})
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```
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## See also
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[set accelerometer range](/reference/input/set-accelerometer-range),
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[compass heading](/reference/input/compass-heading),
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[light level](/reference/input/light-level)
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