# Converting between cartesian and polar coordinates

#### henryc09

1. Homework Statement

Particle is moving with velocity v= ui along the line y=2. What is its v in polar coordinates

2. Homework Equations

3. The Attempt at a Solution
I think I'm being really stupid here but not entirely sure where to start. If you integrate to find position you have it as = ut + c i + 2j and then in polar coordinates is this

r=$$\sqrt{}(ut+c)^2 + 4$$r^? But then if you were to differentiate that the velocity would depend on the initial position which can't be right. I'm obviously doing something wrong and haven't got my head round this topic yet, any help would be appreciated.
1. Homework Statement

2. Homework Equations

3. The Attempt at a Solution

Related Introductory Physics Homework Help News on Phys.org

#### ehild

Homework Helper
$$r=\sqrt{(ut+c)^2 + 4}$$

The polar angle is:

$$\phi=\arctan(\frac{2}{ut+c})$$

The speed in polar coordinates:

$$v=\sqrt{(dr/dt)^2+( r d\phi /dt)^2 }$$

ehild

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving