Simple vector on a train drawing problem

[kirby27]

The problem statement, all vaA ball is hanging from a long string that is tied to the ceiling of a train car traveling eastward on horizontal tracks. An observer inside the train car sees the ball hang motionless.

Draw a clearly labeled free-body diagram for the ball if the train has a uniform velocity.

Draw a clearly labeled free-body diagram for the ball if the train is speeding up uniformly.

-for the first one i drew two vectors. one up. one down with the same magnitude and mastering physics said it was wrong. i don't know why?

 

[PeterO]

The problem statement, all vaA ball is hanging from a long string that is tied to the ceiling of a train car traveling eastward on horizontal tracks. An observer inside the train car sees the ball hang motionless.

Draw a clearly labeled free-body diagram for the ball if the train has a uniform velocity.

Draw a clearly labeled free-body diagram for the ball if the train is speeding up uniformly.

-for the first one i drew two vectors. one up. one down with the same magnitude and mastering physics said it was wrong. i don't know why?

What labels did you use for those two forces? Perhaps that was the problem.