h <- 1 dVdt <- 5
r <- 1 cat(dVdt/(2* pi* r), "cm/s")
## 0.7957747 cm/s
r <- 10 cat(dVdt/(2* pi* r), "cm/s")
## 0.07957747 cm/s
r <- 100 cat(dVdt/(2* pi* r), "cm/s")
## 0.007957747 cm/s