# Homework Help: Pseudo forces

1. Feb 18, 2015

### erisedk

1. The problem statement, all variables and given/known data
A bob of mass m is suspended from the ceiling of a train moving with an acceleration g/√3
(a) If an observer is sitting inside the train, what angle with the vertical will he observe?
(b) If an observer is standing on the platform, what angle will he observe?

2. Relevant equations

3. The attempt at a solution
I know that the angle is 30 degrees (after taking the pseudo force into account), but I'm not sure if this is the answer for both parts or just (b)?

2. Feb 18, 2015

### lightgrav

If there is a protractor sticking down from the train's ceiling, will the 2 observers agree with the rope's alignment?

3. Feb 18, 2015

### erisedk

I don't know, that's the issue.

4. Feb 18, 2015

### lightgrav

One guy sees the rope in front of (obscuring) the 30° mark ... how could the other guy see a different number being blocked?
The light either gets blocked, or it doesn't.

5. Feb 18, 2015

### erisedk

So they both see the same thing. Okay!