# Inertial or not inertial

1. Mar 16, 2013

### Bostonpancake0

You are conducting an experiment inside a train car that may move along level rail tracks. A load is hung from the ceiling on a string. The load is not swinging, and the string is observed to make a constant angle of with the horizontal. No other forces are acting on the load. Which of the following statements are correct?

1./train is an inertial reference frame
2./train is not an inertial reference frame
3./train may be instantaneously at rest
4./The train may be moving at a constant speed in a straight line.
5./ The train may be moving at a constant speed in a circle.
6./The train must be speeding up.
7./The train must be slowing down.
8./The train must be accelerating

I'm thinking 2./ and 8./ as the angle of 45 degrees indicates a force acting on the load, thus meaning that the train is not an inertial reference frame, but I'm not totally shore if I am on the right track??

2. Mar 16, 2013

### SammyS

Staff Emeritus
Where does 45° suddenly come from ?

3. Mar 16, 2013

### Bostonpancake0

ohhhh and 5./ as train can be in ciruclar motion causing an centripetal acceleration causing 45 degree angle of load and is still a non -inertial reference frame.

4. Mar 16, 2013

### Bostonpancake0

it must come from an acceleration right?

5. Mar 16, 2013

### SammyS

Staff Emeritus
I see nothing regarding 45° in the problem statement .

6. Mar 16, 2013

### OCR

I not shore you're on the left track, either...

It might be that the train car is now buoyed up by the water you've entered, when leaving the shore...

Iff this is the case, you are in a non-inertial reference frame.

The 45° string angle could indicate you are about to turn turtle, in which case 3./ will shorely apply...

OCR... :tongue2:... lol

Last edited: Mar 16, 2013