# Homework Help: Angular Position

1. Nov 5, 2008

### Nyx018

This is the problem:
During a certain period of time, the angular position of a swinging door is described by θ = 4.92 + 10.7t + 1.91t2, where θ is in radians and t is in seconds. Determine the angular position, angular speed, and angular acceleration of the door at the following times.

then I'm given for part a) t=0s and part b) is t=3.07s

I know I have to use the equation for angular position s=r$$\theta$$ then derive that once for angular velocity ($$\omega$$) then take the second derivative for angular acceleration ($$\alpha$$). I just don't understand what the values for s and r are and where the come from within this problem. i have that $$\theta$$(0)=4.92 or .0859rad

any help or guidance is much appreciated.

2. Nov 5, 2008

### heth

s is the linear position.

Theta is the angular position (as described in the question).

That should get you started off.

3. Nov 6, 2008

### Nyx018

ok I understand that but how do I find out or determine the value of the linear position from the formula theta?

4. Nov 7, 2008

### heth

The part of the question quoted only asks for the angular position (another term for angle), angular speed and angular acceleration. There'd be no need to use s = rtheta at all, just differentiate what you've been given in the question.