Hello, I'm new on mathcad; I'm trying to repeat a physics exercise founded online.
I think It was builded using an old version.
My firest problem is the F assignation: as far I have understood, in the picture values from table are assigned to F. If I try to do that I get a red square mark as missing value for F.
What am I missing?
ACCEPTED SOLUTION
Accepted Solutions
The picture shows something done in Mathcad 15 or older. To input the data and assign it to F the option "Insert-Data-Table" was used. This convenient way is not available in Prime, which I assume is what you are using.
Prime has a lot of limitations and drawbacks compared to the older real Mathcad, but in your case this can be fixed quite easily. Simply use a matrix and assign it to variable F and not a table. Tables in Prime are something completely different as they were in Mathcad.
You can create a matrix by typing Ctrl-M or via the appropriate menu. You enter a value and pressing Crtl-Space adds a second column. With Ctrl-Enter you can add rows to type in your numbers.
But ... if you really want to do so, you can also use a Prime table to input your data.
Use the menu ribbon "Matrices/Tables" - "Insert Table", chose a table with two columns and some rows (you always can add rows by pressing Ctrl-Enter). The headers of your tables must be named F<0> and F<1>, whereas F<0> means using the column selector you get by pressing Ctlr-C after typing F.
As you are using Mathcad/Prime I would suggest using units and meaningful names right from the start. You can do this by assigning the distance and velocity values separately to single vectors or by using a Prime table the way shown in the pic below. I guess there is no need anymore for the combined matrix F, but if you really need it you can always use F:=augment(dist, FSmooth). BTW, the latter would not be possible in older Mathcad versions because they won't allow values of different dimensions (length, speed) in one matrix. So even though Prime is quite inferior to the older Mathcad versions on the whole, it does have a few advantages here and there.
Prime6 sheet attached
The picture shows something done in Mathcad 15 or older. To input the data and assign it to F the option "Insert-Data-Table" was used. This convenient way is not available in Prime, which I assume is what you are using.
Prime has a lot of limitations and drawbacks compared to the older real Mathcad, but in your case this can be fixed quite easily. Simply use a matrix and assign it to variable F and not a table. Tables in Prime are something completely different as they were in Mathcad.
You can create a matrix by typing Ctrl-M or via the appropriate menu. You enter a value and pressing Crtl-Space adds a second column. With Ctrl-Enter you can add rows to type in your numbers.
But ... if you really want to do so, you can also use a Prime table to input your data.
Use the menu ribbon "Matrices/Tables" - "Insert Table", chose a table with two columns and some rows (you always can add rows by pressing Ctrl-Enter). The headers of your tables must be named F<0> and F<1>, whereas F<0> means using the column selector you get by pressing Ctlr-C after typing F.
As you are using Mathcad/Prime I would suggest using units and meaningful names right from the start. You can do this by assigning the distance and velocity values separately to single vectors or by using a Prime table the way shown in the pic below. I guess there is no need anymore for the combined matrix F, but if you really need it you can always use F:=augment(dist, FSmooth). BTW, the latter would not be possible in older Mathcad versions because they won't allow values of different dimensions (length, speed) in one matrix. So even though Prime is quite inferior to the older Mathcad versions on the whole, it does have a few advantages here and there.
Prime6 sheet attached
I'm facing other iusses, I think because of differeces from the 2 version of Mathcad.
Here the old :
and attached my file.
Here the errors:
and I can't find the meaning/equivalent for the "vertical line symbol" in the a(v1) assignement.
I'm trying to understand what the guy that wrote it has done, but it's hard if I can't make a working example.
1) You missed an "i" when you defined v2 after N:=50 and i:=0..N
2) This is already a problem in the original source. v2 is used twice in the sheet. On top its a vector with 121 elements but later it should be a vector with N+1 elements (and of course with different meaning and different values). You defined N:=50 and so only the first 51 elements of the former vector where overwritten, but the remaining 70 are not deleted that way and this has a strange effect when you later plot 😉
You may either chose a different variable name, redefine v2 to something like v2:="dummy" before you assign the new vector values or use clear(v2) to delete the variable (I have chosen the latter in the sheet attached).
3) C.D is a function with four arguments. You can't plot just the function name C.D over the vector v2/V.S. What should be at the y-axis is the vector C.D0 which is the function C.D evaluated with the velocity vector v2 and the correct air density, area and force values of the bullet.
Note that in the plot you can edit the first, second and last value at each axis to change the tick marks as needed.
One word of caution! The whole calculation depends on just six data points (dist, FSmooth). I guess that the table sure should run up to 1200 yards and is not intended to stop at 250 or 300 yards. The values are not seen in the picture you are working from.
Based on these six points a cubic spline interpolation function v(x) was created but the values it returns for inputs larger than 250 yd can in no way be relied upon!
After that using this interpolating function, a greater number of x- and y-values (121) was calculated, that pile of dots was then smoothed using supsmooth and based on these new points again an interpolation function (named v2 again) was defined. I would call this voodoo and I don't think that it helps anything.
The plot below shows the six initial data points in red. The thin blue line is the first interpolation function based on only these six points (to be able to compare them I renamed it v_(x)). The underlying thick orange line is the function v(x) after applying the aforementioned voodoo spell.
I can spot not improvement or significant difference. I guess you happily could delete all of these regions
and use the initially created function v(x) right ahead.
But in any case you have to provide more reliable input values for distances larger than 250 yd up to 1200 yd !!
If not, the whole calculation seems to make no sense. I guess the velocity is not supposed to get negative after a distance of approx. 800 yd but thats the case if you use this interpolation function for extrapolation beyond 250 yd.
I guess that the initial values should rather look something like this (I just added a low, but positive velocity value for the distance 1200 yd):
Of course this also affects the values in the last plot
