- #1

yucheng

- 213

- 57

- Homework Statement:
- N/A

- Relevant Equations:
- N/A

Newton's laws only hold in intertial frames. In general, the center of mass (CM) is accelerating, so it cannot be used as a frame. However,

1. Suppose that CM is accelerating only in the ##\hat{z}## direction. Does this mean that the CM frame is still valid in the ##\hat{x}## and ##\hat{y}## direction?

2. For rotation, suppose we want to find the torque about the CM, and the CM is acclerating in the ##\hat{x}## direction. We find that a torque about CM as origin, ##\tau = f \hat{z}## Is this then a valid frame of reference for torques as long as they are not in the same direction as the acceleration?

Context(Kleppner and Kolenkow, Problem 7.6:

So the author found the torques around the CM (the black dot), and since the person is moving around a circular track, there is a centripetal acceleration acting on the CM, and so it should not be inertial.

P.S. actually, any point that is accelerating with the conditions given, not just CM.

Thanks in advance!

1. Suppose that CM is accelerating only in the ##\hat{z}## direction. Does this mean that the CM frame is still valid in the ##\hat{x}## and ##\hat{y}## direction?

2. For rotation, suppose we want to find the torque about the CM, and the CM is acclerating in the ##\hat{x}## direction. We find that a torque about CM as origin, ##\tau = f \hat{z}## Is this then a valid frame of reference for torques as long as they are not in the same direction as the acceleration?

Context(Kleppner and Kolenkow, Problem 7.6:

So the author found the torques around the CM (the black dot), and since the person is moving around a circular track, there is a centripetal acceleration acting on the CM, and so it should not be inertial.

P.S. actually, any point that is accelerating with the conditions given, not just CM.

Thanks in advance!

Last edited: