How to Find the Modulus of Velocity and Acceleration?

[ritwik06]

Homework Statement

The radius vector of a point depends on time t, as $$\vec{r}=\vec{c}t+\vec{b}\frac{t^{2}}{2}$$, where $$\vec{c}$$ and $$\vec{b}$$ are constant vectors. Find the modulus of velocity and acclereation at any time t.

The Attempt at a Solution

$$\vec{v}=\vec{c}+\vec{b}t$$

$$\vec{a}=\vec{b}$$

But how shall I find the modulus?

 

[Dick]

The modulus of a vector v is the square root of v dot v.