Class 4: falling bodies

falling cat

y <- rep(NA, 20) # empty vector to store result
i <- 1       # time
y[i] <- 10   # initial vertical position
while(y[i]>0) {  # while we don't hit the floor...
    i <- i+1 # time passes
    y[i] <- y[i-1] + -1 # update position
}        # ..and repeat
plot(y)      # draw all positions

Bounce

N <- 60
y <- rep(NA, N) # initialize to empty
y[1] <- 120 # initial position
speed <- -20    # initial speed
for(i in 2:N) { # as time passes...
    y[i] <- y[i-1] + speed # update position
    if(y[i] < -180){    # if we hit the floor
        speed <- -1*speed # bounce
    }
    if(y[i] > 180){ # if we hit the ceil
        speed <- -1*speed # bounce
    }
}
plot(y)

Boolean bounce

N <- 60
y <- rep(NA, N) # initialize to empty
y[1] <- 120 # initial position
speed <- -20    # initial speed
for(i in 2:N) { # as time passes...
    y[i] <- y[i-1] + speed # update position
    if(y[i] < -180 | y[i] > 180){ # if we hit the floor or ceil
        speed <- -1*speed # bounce
    }
}
plot(y)

gravity

N <- 60
y <- rep(NA, N) # initialize to empty
y[1] <- 120 # initial position
speed <- -20    # initial speed
for(i in 2:N) { # as time passes...
    y[i] <- y[i-1] + speed # update position
    if(y[i] < -180 | y[i] > 180){ # if we hit the floor or ceil
        speed <- -1*speed # bounce
    }
}
plot(y)