Solving for a Train Without Knowing Mass

[kmm0830]

A train is traveling up a 3.73 degree incline at 3.25 m/s when the last car breaks free and begins to coast without friction. A) How long does it take for the last car to come to rest momentarily? B) How far did the last car travel before coming to rest?



Newtons Second Law



I know that you must use Newton's second law here, but do not understand how to solve this problem without knowing the mass of the train to determine how long it will take for it to stop.

 

[tiny-tim]

welcome to pf!

hi kmm0830! welcome to pf!

I know that you must use Newton's second law here, but do not understand how to solve this problem without knowing the mass of the train to determine how long it will take for it to stop.

standard trick …

call the mass "m", and carry on anyway …

you'll find that m will cancel out at the end! ​