Modulus of speed

[dopey9]

Homework Statement

i just want to know what the modulus of the speed (u) would if

Homework Equations

u = (-2/r)er + (2/r)etheta

The thing is i get confused with the er and etheta ..do these just mean the direction...this topic is fluid mechanics

The Attempt at a Solution

i reckon the answer is square root 8/r ...as i reckon the e's dont get affect...can some one verify this

Homework Statement

Homework Equations

The Attempt at a Solution

Homework Statement

Homework Equations

The Attempt at a Solution

 

[Mindscrape]

The e_r and e_theta are directions in plane polar coordinates.