g =  9.8  # m/s^2
v0 =   0  # m/s
v1 =  50  # m/s
v2 =  10  # m/s

tau1 = v1 / g
tau2 = v2 / g

plot(0, 0,  xlim=c(0, 6*tau1+10*tau2), ylim=c(0,v1), col='blue',
     xlab = 't (s)', ylab='v (m/s)')
np = 50
t1 = seq(0, 6*tau1, len=np)
Dt = 6*tau1/np
for (i in 1:length(t1)) {
  Sys.sleep(Dt)
  points(t1[i], v1 + (v0-v1)*exp(-t1[i]/tau1), col='blue')  
}

t2 = seq(0, 10*tau2, len=10*tau2/Dt)
for (i in 1:length(t1)) {
  Sys.sleep(Dt)
  points(max(t1)+t2[i], v2 + (v1-v2)*exp(-t2[i]/tau2), col='blue' )
}