Calculating Distance for a Train on a 1% Grade

AI Thread Summary
A 60,000 kg train on a 1% grade experiences a friction force of 4,000 N and starts at 12 m/s, aiming to determine the distance it travels before slowing to 9 m/s. The expected distance is 191.2 m, but one participant calculated it as 472.5 m using the formula for force and acceleration. The discussion highlights the need to calculate acceleration, which is not provided, and emphasizes understanding the forces acting on the train. Participants suggest using kinematic equations to relate the initial and final velocities to the distance traveled. The conversation revolves around clarifying the assumptions about the train's motion and the forces involved.
A_Sushi
Can anyone help with the following question, please?
1.
A 60,000kg train is being pulled up a 1 percent grade (it rises 1m for each horizontal 100m). The friction force opposing the motion of the train is 4,000N. Initial speed of the train is 12 m/s. Through what horizontal distance will the train move before its speed is reduced to 9m/s?
3.
The answer suppose to be 191.2 m. I got 472.5 m as follows:
Fd=m*(v2-v2)/(2*distance)
4 000 = (60 000*(92-122)) / (2*distance) = 472.5 m
 
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Use the kinematic equation:

##\Delta x=\dfrac{v_f^2-v_i^2}{2a}##

You are given the initial and final velocities...what is the acceleration? How does ##\Delta x## relate to the horizontal distance?
 
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Likes MarkFL
MarkFL said:
Use the kinematic equation:

##\Delta x=\dfrac{v_f^2-v_i^2}{2a}##

You are given the initial and final velocities...what is the acceleration? How does ##\Delta x## relate to the horizontal distance?
The acceleration is not given. I do not know how to calculate the acceleration
 
A_Sushi said:
how to calculate the acceleration
Even though it says the train is being pulled up, I think you have to assume there is no engine attached, it is just coasting.
What are the forces on the train? What equation can you write relating those to acceleration?
 
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