I tried to solve the following problem by finding the roots of the quadratic and modelling the speed of sound with the equation -&gt; (y=-380x+100). I found the x intercept for the linear equation, and decided that the person escaped because it's x intercept was less than that of the quadratic. (meaning the sound got to the person before the cannon did, giving them time to run). Is this the correct way of solving the problem? A cannonball is launched from a point 100 m above ground, at a speed of 20 m/s. This is modelled by the equation h(t)=-4.9t****2 +20t +100 The speed of sound (of the cannonball is) 380m/s If a person sitting directly underneath the cannonball runs as soon as they hear the sound do they escape the cannon? My main question is &quot; y=-380x+100&quot; the correct equation to model the cannon's sound?
A cannonball is launched from a point 100 m above ground, at a speed of 20 m/s. This is modelled by the equation $h(t)=-4.9t^2 +20t +100$ The speed of sound (of the cannonball is) 380m/s If a person sitting directly underneath the cannonball runs as soon as they hear the sound do they escape the cannon? My main question is &quot;$y=-380x+100$&quot; the correct equation to model the cannon's sound?
How do "Dummy Variables" work? I do not understand how dummy variables work in math.   Suppose we have:  $$I_1 = \int_{0}^{\infty} e^{-x^2} dx$$  How is this equivalent to:  $$I_2 = \int_{0}^{\infty} e^{-y^2} dy$$  How does this dummy variable system work?   Since $y$ is the dependent variable for $I_1$ How can $y$ itself be and independent variable for $I_2$  ??  Thanks! My users are sending me point data that were digitized using Google Earth. How can I convert their KML to a shapefile and vice versa? How to insert text into a root-owned file using sudo? What's the difference between absolute path &amp; relative path when using any web server or Tomcat? I am trying to burn a shapefile to a raster using GDAL's RasterizeLayer. I pre-create an area of interest raster from a different shapefile, given a specific pixel size. This AOI then serves as a base for all following rasterizations (same number of collumns and rows, same projection and geotransform).  The issue occurs, however, when I go to burn the shapes to their own raster, based on the same pixel size and projections. The link below (don't have enough rep to post the image), shows the original shapefile in tan, and the dark pink where RasterizeLayer has burned data. The light pink is nodata values for the dark pink raster data. The grey is the AOI based on which the shapefile burn was completed.  Given the extents of the shapefile polygons, I would expect to see burn values in the bottom two corners, as well as the two pixels underneath the data that does show. Obviously, however, this is not the case.    As follows is the code that I used to generate these. All of the shapes were created using QGIS, and were all created in the same projection.  (It should be noted that the gridding in the picture shown was just to give an idea of the pixel size I was using.)  from osgeo import ogr from osgeo import gdal  aoi_uri = 'AOI_Raster.tif' aoi_raster = gdal.Open(aoi_uri)  def new_raster_from_base(base, outputURI, format, nodata, datatype):      cols = base.RasterXSize     rows = base.RasterYSize     projection = base.GetProjection()     geotransform = base.GetGeoTransform()     bands = base.RasterCount      driver = gdal.GetDriverByName(format)      new_raster = driver.Create(str(outputURI), cols, rows, bands, datatype)     new_raster.SetProjection(projection)     new_raster.SetGeoTransform(geotransform)      for i in range(bands):         new_raster.GetRasterBand(i + 1).SetNoDataValue(nodata)         new_raster.GetRasterBand(i + 1).Fill(nodata)      return new_raster  shape_uri = 'activity_3.shp' shape_datasource = ogr.Open(shape_uri) shape_layer = shape_datasource.GetLayer()  raster_out = 'new_raster.tif'  raster_dataset = new_raster_from_base(aoi_raster, raster_out, 'GTiff',                                 -1, gdal.GDT_Int32) band = raster_dataset.GetRasterBand(1) nodata = band.GetNoDataValue()  band.Fill(nodata)  gdal.RasterizeLayer(raster_dataset, [1], shape_layer, burn_values=[1])   Is this a bug in GDAL, or is RasterizeLayer burning data based on something other than just the presence or lack of a polygon within a specified pixel area?  The files that I was using can be found . Why can I see the output of background processes? For example, when I type ping 8.8.8.8 &amp;, why can we see ping process working? And when I type find / -name '*test*' &amp; , it's also seen on monitor.  Why is that? Is it not really in background? Is it possible to redirect all of the output of a Bourne shell script to somewhere, but with shell commands inside the script itself? Redirecting the output of a single command is easy, but I want something more like this: #!/bin/sh if [ ! -t 0 ]; then     # redirect all of my output to a file here fi  # rest of script...  Meaning: if the script is run non-interactively (for example, cron), save off the output of everything to a file.  If run interactively from a shell, let the output go to stdout as usual. I want to do this for a script normally run by the FreeBSD periodic utility.  It's part of the daily run, which I don't normally care to see every day in email, so I don't have it sent.  However, if something inside this one particular script fails, that's important to me and I'd like to be able to capture and email the output of this one part of the daily jobs. Update: Joshua's answer is spot-on, but I also wanted to save and restore stdout and stderr around the entire script, which is done like this: # save stdout and stderr to file  # descriptors 3 and 4,  # then redirect them to &quot;foo&quot; exec 3&gt;&amp;1 4&gt;&amp;2 &gt;foo 2&gt;&amp;1  # ...  # restore stdout and stderr exec 1&gt;&amp;3 2&gt;&amp;4 How can I turn off the shrine indicator (or make it stop beeping)? Showing that $\lnot Q \lor (\lnot Q \land R) = \lnot Q$ without a truth table I've done a truth table after reducing it to this and it seems to be equal to $\neg Q$:  $$\lnot Q \lor (\lnot Q \land R) = \lnot Q$$  But when I try to show it without a truth table (with just transformations), I end up in a loop between that and:  $$\lnot Q \land (\lnot Q \lor R)$$  Is there a way to show this is true without using a truth table? What am I missing?!  Thanks in advance! Are there guidelines on how much free RAM a phone should have - specifically Samsung Galaxy S? Arrow keys, Home, End, tab-complete keys not working in shell I have installed ubuntu minimal(mini.iso) on my vm. I then used recovery mode to login as root and create an account with useradd -m admin and then set a password with passwd admin.  When I login on the new account, instead of the normal prompt I only see a $ sign. If I try to tab-complete a command or file name it prints a normal tab. If I try to use the arrow keys it prints ^[[A, ^[[B, ^[[C or ^[[D. Also, ls no longer adds colors.  None of these problems were in recovery mode. How can I fix this? Is it possible to prevent DHCP service on SBS 2003 from shutting down due to rogue DHCP server? Dropping one of the columns when using one-hot encoding My understanding is that in machine learning it can be a problem if your dataset has highly correlated features, as they effectively encode the same information.  Recently someone pointed out that when you do one-hot encoding on a categorical variable you end up with correlated features, so you should drop one of them as a "reference".  For example, encoding gender as two variables, is_male and is_female, produces two features which are perfectly negatively correlated, so they suggested just using one of them, effectively setting the baseline to say male, and then seeing if the is_female column is important in the predictive algorithm.  That made sense to me but I haven't found anything online to suggest this may be the case, so is this wrong or am I missing something?  Possible (unanswered) duplicate: Traverse a list in reverse order in Python How to enable default file manager(nautilus) to handle desktop icons Screen goes white when posting a comment Since iOS 11.2 all the way through 12.2 beta 4, if you post or discard a comment on any post on any SE community, the screen will turn white. This has been ongoing continuously for a year now, and it affects both the SE app and the SO app.   You can go back to the previous screen and open the question again, and everything appears as normal. You can also rotate the screen to get the text to come back. Using the arrows to navigate between the question and answers updates the HUD, but the screen remains white unless one of the above is done to get the text back.        UPDATE: After posting anything (comment, answer), the screen goes all white except for the sidebar. Perhaps it is intentional, but I prefer last week’s behavior of going back to the content. Not major, since the sidebar icons still work. Are neutrinos affected by electromagnetic forces? I know they don't interact with matter nor any electromagnetic forces, but I know they have mass, very little mass but they have. When something has mass it must be attracted by gravity and other objects (electromagnetic) right? extended stars-and-bars problem(where the upper limit of the variable is bounded) The problem of counting the solutions $(a_1,a_2,\ldots,a_n)$ with integer $a_i\geq0$ for $i\in\{1,2,\ldots,n\}$ such that $$a_1+a_2+a_3+....a_n=N$$ can be solved with a stars-and-bars argument. What is the solution if one adds the constraint that $a_i\leq r_i$ for certain integers $r_1,\ldots,r_n$?  e.g. for $n=3$, $N=6$ and $(r_1,r_2,r_3)=(3,3,2)$, the tuple $(a_1,a_2,a_3)=(2,3,1)$ is a solution, but $(2,1,3)$ is not a solution because $a_3=3&gt;2=r_3$. Is there a way in photoshop to convert k values to alpha values? Basically, I would like to make it so that the lighter a pixel is (the more white it has) the more transparent it becomes. Black pixels would be opaque, white pixels would be transparent.  I currently use the slider in blending options on the first tab to get rid of the white and make it transparent but find it works slightly better if I use the magic wand tool with delete.  I figure that there is some blending option out there but there are so many and I'm not sure which to use to achieve my goal.  (Using Photoshop CS6) Is QImage able to open and render pure 16-bit images?