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Script to calculate the most important quantitative information of the drag parabolic shot in International System of Units.Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.
If you want to use another system of units you can do it by making some simple changes.
This is a first approach to the problem and is totally perfectible.
To calculate the maximum range, a transcendental equation is solved regularly, but here we did a first run with a number of time values left over to approximate the time index for which the vertical position becomes zero.
Inputs of the function are:
a) initial velocity vo (scalar) [m/s]
b) shot angle alfa [degrees]
c) (drag coefficient / mass) = b [m^-1]
Parameter
g) gravity acceleration g = 9.81 [m/s^2]
The outputs of the function are:
T_1: ascending time [s]
H: maximum height [m]
L: maximum horizontal range [m]
We need to calculate:
x: horizontal position at time t [m]
y: vertical position at time t [m]
vox: horizontal initial velocity [m/s]
voy: vertical initial velocity [m/s]
drag_parabolic <- function(vo, alpha, b){
g <- 9.81
an <- (2*pi*alpha)/360
vox <- vo*cos(an)
voy <- vo*sin(an)
T_1 <- (1/b)*log(1+(b*voy/g))
H <- (voy/b)-((g/b^2)*log(1+(b*voy/g)))
# first run
t <- seq(0, 25, 1/10)
x <- vector()
y <- vector()
x <- (vox/b)*(1-exp(-b*t))
y <- ((1/b)*((g/b)+voy)*(1-exp(-b*t)))-((g/b)*t)
# time index of max. range
a_T <- which(y < 0)[1]-1
# second run
t_t <- head(t, a_T)
xx <- vector()
yy <- vector()
xx <- (vox/b)*(1-exp(-b*t_t))
yy <- ((1/b)*((g/b)+voy)*(1-exp(-b*t_t)))-((g/b)*t_t)
R <- round(xx[length(xx)],2)
H <- round(H,2)
plot(xx, yy, xlab=”X”, ylab=”Y”, type = “o”, col = “blue”, axes=F)
axis(1, at = seq(0,R,R/10),labels = seq(0,R,R/10), cex.axis = 0.7)
axis(2, at = seq(0,H,H/10),labels = seq(0,H,H/10), cex.axis = 0.7)
print(“Initial Velocity”);print(paste(vo,”m/s”))
print(“Angle of Shot”);print(paste(alpha,”degrees”))
print(“Ascending Time”);print(paste(T_1,”s”))
print(“Maximum Height”);print(paste(H,”m”))
print(“Aprox. Max. Range”);print(paste(R,”m”, “+-2%”))
legend(R/3, H/2, legend = c(paste(“vo =”, vo, “m/s”),
paste(“alpha =”, alpha,”degrees”),
paste(“Ascending time”, paste(T_1,”s”)),
paste(“Maximum height”, paste(H,”m”)),
paste(“Aprox. Max. Range”, paste(R,”m”,”+-2%”))),
cex=0.7, bg = par(“bg”))
title(main = “Drag Parabolic Shot”, sub = “”)
}
Let’s try the function:
drag_parabolic(50, 45, 0.5)
We compare with a simple parabolic shot with the same parameters:
I will be glad to receive your comments and suggestions to improve the script.
Get the script in:
https://github.com/pakinja/Data-R-Value
To leave a comment for the author, please follow the link and comment on their blog: Data R Value.
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