Why Does a Balloon Swing Forward When a Train Decelerates?

[moneenfan]

you are on a train moving along a track at constant velocity. hanging from a switcase in an overhead luggage compartment is a balloon the end of a string. as long as the train continues at constant speed you observe the string is vertical . as you neer your destination you obsrve the ball swing forward slowly and come to rest at an angle of 8 degrees from the vertical

im having trouble understanding this.Im not sure if the ball is accelerating relative to the ground or not. I think it is. And I am not too sure how i would approach solving for the acceleration of the ball. Any ideas? I really want to better comprehend the question.

 

[diazona]

What does the question ask you to find?

 

[moneenfan]

when it comes to rest at 8 degrees from the vertical the ball is stationary with respect to you. is it acceleration relative to the ground? What evidence do you have for or against the ball accelerating relative to the ground?

based on your observations the ball is the reference frame of the train, an inertial reference frame while the ball is hanging from the angle from the vertical. Explain?

What is the acceleration of the ball and what does this tell you about the motion of the train?

 

[diazona]

OK, well first of all: why does the ball not hang straight down?

 

[moneenfan]

well it does to begin with, but as the train begins to decelerate we have a change in velocity and it begins to accelerate negatively. We no longer maintain constant velocity and zero acceleration. Could it be that the ball while at constant velocity maintains itself relative to the floor of the trai and not the ground because there is zero acceleration?