Velocity gradient
= \(\frac{dv}{dx}\)
⇒ Dimensions are
\(\frac{[LT-1]}{[L]}=[T-1]\)
Decay constant \(λ\) has dimensions of \([T^{–1}]\) because of the relation
\(\frac{dN}{dt} = -λN\)
⇒ Velocity gradient and decay constant have same dimensions.
The rate at which an object covers a certain distance is commonly known as speed.
The rate at which an object changes position in a certain direction is called velocity.

Read More: Difference Between Speed and Velocity