Solving for a Train Without Knowing Mass

AI Thread Summary
To solve the problem of a train coasting up an incline after losing its last car, Newton's second law can be applied without needing the mass of the train. By assigning the mass a variable "m," calculations can proceed, and the mass will ultimately cancel out in the equations. This approach allows for determining both the time it takes for the last car to come to rest and the distance it travels before stopping. The incline's angle and initial speed are key factors in the calculations. Thus, the problem can be solved effectively without knowing the train's mass.
kmm0830
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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.
 
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welcome to pf!

hi kmm0830! welcome to pf! :smile:
kmm0830 said:
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! :wink:​
 

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