What is the displacement of an ion in a mass spectrometer?

[negation]

Homework Statement

An ion in a mass-spec follows a semicircular path of radius 15.2 cm.
a)What are the distance it travels
b)The magnitude of its displacement

The Attempt at a Solution

a) s = pi.r
r = 15.2cm
∴
s = pi(15.2cm)

b) what is part(b) asking?

 

[negation]

Ok I think I had it figured out.

particle at position(15.2,15.2)
Pythagoras theorem should solve it.