Radians: Negative 126 Answer Explained

  • Thread starter goonking
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In summary, the discussion revolves around the direction of rotation for a wagon moving in the +x direction. The solution provided was 126 radians, but it was supposed to be -126 radians. The convention for the sign of rotation in planar coordinates is usually anticlockwise positive. It is mentioned that it could be made clearer that a signed value is needed, not just a magnitude. The wheels will rotate clockwise and it is asked what is usually taken as the positive direction for rotation in the plane. The response is that the standard convention is anticlockwise positive, even though it was initially thought that it didn't matter which direction was set as positive or negative.
  • #1
goonking
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Homework Statement


upload_2015-3-26_21-30-49.png


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?
 
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  • #2
goonking said:
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.)
 
  • #3
haruspex said:
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.
 
  • #4
goonking said:
wheels will rotate clockwise.
Yes, and what is usually taken as the positive direction for a rotation in the plane?
 
  • #5
haruspex said:
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.
 
  • #6
goonking said:
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.
 

1. What is a radian?

A radian is a unit of measurement for angles, representing the amount of rotation an object undergoes around a fixed point. It is defined as the angle created by two radii of a circle that intercept an arc equal in length to the radius.

2. What does a negative 126 radian measure?

A negative 126 radian measures an angle that is equivalent to rotating counterclockwise by 126 radians, or about 7255 degrees. It is important to note that angles measured in radians can be either positive or negative, depending on the direction of rotation.

3. How is a negative 126 radian calculated?

To calculate a negative 126 radian, you can use the formula:
angle in radians = (angle in degrees * pi) / 180
In this case, it would be:
(-126 * 3.14159) / 180 = -2.19911 radians

4. Can an angle be both positive and negative in radians?

Yes, an angle can be both positive and negative in radians. This is because radians measure the direction of rotation, and an angle can rotate in either a clockwise (positive) or counterclockwise (negative) direction.

5. How do you convert radians to degrees?

To convert radians to degrees, you can use the formula:
angle in degrees = (angle in radians * 180) / pi
In this case, it would be:
(-2.19911 * 180) / 3.14159 = -126 degrees

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