```
Projectile motion was interesting for me in grade 11 Physics. Unfortunately at the time we did
not have an experimental activity that could prove to me that the calculations work. However,
later in grade 12 my group used projectile motion calculation to determine the angle for our model rocket
to fly the furthest (optimal angle is 45 degrees for furthest displacement). Sever years later I figured a
trajectory could be plotted using gnuplot Fortran. The internet probably has little or no
use of this graph but I like its clean and simple look from gnuplot so here goes the graph for
an object thrown at 45 degrees with 10 m/s
velocity.
1: !************************************************
2: !This program plots projectile motion of an object.
3: !The program requires user input for initial velocity
4: !and angle of the object.The algorithm uses a time
5: !step of 0.01 second i.e. it calculates object's
6: !location in the x and y plane every 0.01 second.
7: !**********By: Waleed Ishaque, 2013**************
8: program projectile_plot
9: implicit none
10: !Defining constants:
11: real, parameter :: pi = 3.142
12: real :: u, a, t
13: real, parameter :: g = 9.8
14: real:: x(150),y(150)
15: !where g is gravity, pi is "pi"
16: !u is object's initial velocity
17: !a is object's initial angle
18: !t is time during the simulation
19: !x and y are arrays with 150 rows
20: !Seek user input
21: write(*,*) 'Enter angle of projectile'
22: read*, a
23: write(*,*) 'Enter velocity of projectile'
24: read*, u
25: !Convert angle to radians
26: a = a*pi/180.0
27: !open .dat file and start writing on it using the algorithm
28: open(1, file='proj.dat')
29: integer :: i
30: do i=1,100
31: !displacement of object in x and y direction
32: t = (i*0.01)
33: x(i) = u*cos(a)*t
34: y(i) = u*sin(a)*t - 0.5*g*t*t
35: !write output in file "proj.dat" for plotting
36: write(1,*) x(i), y(i)
37: !kill the loop when the object hits the ground
38: if (y(i)<0) exit
39: end do
40: close(1)
41: !close file
42: end program projectile_plot
```