# Calculating vectors

1. Jan 29, 2007

### tnhoots

1. The problem statement, all variables and given/known data
1)A skater glides along a circular path of radius 4.90m.
a)if he coasta around one half of the circle, find the magnitude of the displacement vector
b)find how far the person skated
c)What is the magnitude of displacement if he skates all the way around the circle

2. Relevant equations
Area of a circle = pi(radius squared)

3. The attempt at a solution

-My first inclination for part a was to find the area of the circle and then multiply that by the degrees of one half the circle (180) and then do the same for c but multiply by (360). I am unsure of b. Is that the right path.

2. Jan 29, 2007

### Kurdt

Staff Emeritus
You are not really on the right lines. What is the definition of displacement? For part b you need to find the distance the person has skated. Since they skated half the circumference of a circle this should be easy to find.

3. Jan 29, 2007

### tnhoots

part c

I found the solution to these problem, except for part c. When he had skated half way around the circle, he had gone 9.80m. So wouldn't he have gone 19.6m when he skated completely around the circle?

4. Jan 29, 2007

### Kurdt

Staff Emeritus
When he travelled all the way round the circle his displacement would not be 19.6m. Remember displacement is a vector which specifies the position of a particle with reference to an origin or a starting point. If he returns to the starting point then what will the magnitude of the displacement vector be?