# Function to Simulate Parabolic Shot with Drag.

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Script to calculate the most important quantitative information of the drag parabolic shot in International System of Units.**Data R Value**, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)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

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)))

**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

x <- vector()

y <- vector()

x <- (vox/b)*(1-exp(-b*t))

y <- ((1/b)*((g/b)+voy)*(1-exp(-b*t)))-((g/b)*t)

**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)

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”))

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

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