Radians: Negative 126 Answer Explained

[goonking]

Homework Statement

Homework Equations

The Attempt at a Solution

So, I got the answer to be 126 radians BUT my answer was wrong because it was suppose to be NEGATIVE 126 radians. Can someone explain why my answer was suppose to be negative?

 

[haruspex]

Can someone explain why my answer was suppose to be negative?

The wagon is moving in the +x direction. Which way will the wheels rotate? What is the usual convention for the sign of a rotation in planar co-ordinates?

(That said, I think it could me made clearer that a signed value is wanted, not just a magnitude.)

 

[goonking]

The wagon is moving in the +x direction. Which way will the wheels rotate? What is the usual convention for the sign of a rotation in planar co-ordinates?

(That said, I think it could me made clearer that a signed value is wanted, not just a magnitude.)

wheels will rotate clockwise.

 

[haruspex]

wheels will rotate clockwise.

Yes, and what is usually taken as the positive direction for a rotation in the plane?

 

[goonking]

Yes, and what is usually taken as the positive direction for a rotation in the plane?

I thought it didn't matter which direction you set to be positive or negative.

 

[haruspex]

I thought it didn't matter which direction you set to be positive or negative.

The standard convention, e.g. in polar co-ordinates, is anticlockwise positive.