Help with kinetic and dynamic principles

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Discussion Overview

The discussion revolves around solving problems related to kinetic and dynamic principles, specifically involving a train moving up an incline and a collision between railway wagons. Participants seek assistance in understanding the relevant formulas and calculations needed to analyze the scenarios presented.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant describes a scenario involving a train of mass 240 tonnes moving up an incline and requests help with calculating the distance traveled before coming to rest, as well as analyzing a collision between two railway wagons.
  • Another participant suggests that knowing the mass and speed allows for the computation of energy, and that energy loss through climbing and friction can be considered constant.
  • There is a mention of the collision being a plastic collision problem, where momentum is highlighted as a useful concept.
  • One participant expresses confusion about the formulas needed and how to derive them, particularly in relation to speed and friction.
  • Participants discuss the resistance to motion, with one calculating the total force acting on the train based on its mass and resistance per tonne.
  • There is a clarification about the incline ratio of 1 in 90, with a participant explaining its meaning in terms of horizontal and vertical displacement.
  • Another participant emphasizes that Newtons are a measure of force and cannot be directly converted into speed, suggesting a focus on energy calculations instead.

Areas of Agreement / Disagreement

Participants generally agree on the need to apply principles of energy and momentum to solve the problems, but there is no consensus on the specific formulas or methods to use. Confusion remains regarding the application of forces and the relationship between force and speed.

Contextual Notes

Participants express uncertainty about the necessary formulas and the interpretation of the incline's effect on the train's motion. There are unresolved questions regarding the conversion of force into speed and the specific calculations required for the scenarios presented.

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a train of mass 240 tonne is moving, at a speed of 84 km/h, up an incline of 1 in 90. the resistance to motion is 45 n per tonne. if power is removed, calculate the distance traveled along the incline before the train comes to rest

and

a railway wagon of mass 10 tonne traveling due east with a velocity of 14 kmh on a straight section of track collides with a second wagon of mass 12 tonne traveling due west at 3 km/h if thery are locked together after impact find the magnitude and direction of their common velocity.
i have no idea how to work it out, my notes have gone missing

i don't know where to begin, can someone help me with it please?
i don't mean do it for me i mean give me help in doing so, be it via email of instant message
 
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shibby_ftw said:
a train of mass 240 tonne is moving, at a speed of 84 km/h, up an incline of 1 in 90. the resistance to motion is 45 n (N of coeff of friction?) per tonne. if power is removed, calculate the distance traveled along the incline before the train comes to rest

and

a railway wagon of mass 10 tonne traveling due east with a velocity of 14 kmh on a straight section of track collides with a second wagon of mass 12 tonne traveling due west at 3 km/h if thery are locked together after impact find the magnitude and direction of their common velocity.

1. Are your notes really missing :P.

2. If you have the mass and speed of an object you can compute it's energy. If you know that it loses energy through climbing and friction (or whatever that is) in a constant manner than time is easy.

3. This is a plastic collision problem and energy will be lost (out of the system) whatever remains will decide your speed. Momentum is more useful in this problem.
 
1. Are your notes really missing :P.

2. If you have the mass and speed of an object you can compute it's energy. If you know that it loses energy through climbing and friction (or whatever that is) in a constant manner than time is easy.

3. This is a plastic collision problem and energy will be lost (out of the system) whatever remains will decide your speed. Momentum is more useful in this problem.[/QUOTE]haha yeahh they are actually missing, i don't know the formula required to work it out, or how towork it out at all. I am really bad at mechanical principles can you show me how to find out the formula to use? are they based on the speed of the train and the friction?

and the resistance to motion is I am guessed its 240 tonne so there is 45N per tonne slowing it down so there's 10800N acting on the train? how are Newtons turned into speed? is it the same as gravity? so 9.81m/s ?and then times 10800? 105948 m/s divided by 1000 to make it km/h acting on the train so 105.948 km/h and its goes 84km/h so its slowing pretty fast? or am i well off?
 
I guess it wants to mean that on 90 units of horizontal offset, there is one unit of horizontal offset.
so tg(alpha)=1/90
 
shibby_ftw said:
haha yeahh they are actually missing, i don't know the formula required to work it out, or how towork it out at all. I am really bad at mechanical principles can you show me how to find out the formula to use? are they based on the speed of the train and the friction?

and the resistance to motion is I am guessed its 240 tonne so there is 45N per tonne slowing it down so there's 10800N acting on the train? how are Newtons turned into speed? is it the same as gravity? so 9.81m/s ?and then times 10800? 105948 m/s divided by 1000 to make it km/h acting on the train so 105.948 km/h and its goes 84km/h so its slowing pretty fast? or am i well off?

U cannot turn everything into everything else. N are a measure of force, not speed. There are relations to energy spentthat will help. First find out what energy the train has at 84 km/h. expressed in joules.
 

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