What is the momentum of an 80 car freight train traveling at 40km/h?

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SUMMARY

The momentum of an 80-car freight train traveling at 40 km/h is calculated using the formula p = mv, where m is the mass and v is the velocity. Given that each car weighs approximately 100,000 kg, the total mass is 8,000,000 kg. Therefore, the momentum is calculated as p = (100,000 kg * 80) * (11.11 m/s) = 88,888,889 kg·m/s. While external forces like friction and drag exist, they do not affect the momentum as long as the train maintains a constant speed due to the engine's balancing force.

PREREQUISITES
  • Understanding of basic physics concepts, specifically momentum.
  • Familiarity with the formula p = mv (momentum = mass x velocity).
  • Knowledge of unit conversions, particularly between km/h and m/s.
  • Basic comprehension of forces such as friction and drag.
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  • Study the principles of momentum in physics, focusing on real-world applications.
  • Learn about the effects of friction and drag on moving objects.
  • Explore the dynamics of train operations and how engines counteract external forces.
  • Investigate advanced momentum calculations involving varying speeds and external forces.
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This discussion is beneficial for physics students, engineers, and anyone interested in understanding the dynamics of large moving objects, particularly in the context of transportation and mechanics.

Tylemaker
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I saw a freight train cruising by today and thought "The momentum of that thing must be mind-blowing". I only have high school physics and thus couldn't calculate the momentum including many external forces. Did some quick research and was wondering what the momentum of an 80 car freight train traveling 40km/h would be? The average car being approximately 110.2 tons or 100,000kg

I came up with:
p=mv
p= (100,000*80)*(11.11...)
p= 88,888,889 kgm/s
Thats a lot of momentum but with friction, drag etc what would it actually be?
 
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Tylemaker said:
I saw a freight train cruising by today and thought "The momentum of that thing must be mind-blowing". I only have high school physics and thus couldn't calculate the momentum including many external forces. Did some quick research and was wondering what the momentum of an 80 car freight train traveling 40km/h would be? The average car being approximately 110.2 tons or 100,000kg

I came up with:
p=mv
p= (100,000*80)*(11.11...)
p= 88,888,889 kgm/s
Thats a lot of momentum but with friction, drag etc what would it actually be?

The momentum is exactly what you calculated it to be. Friction and drag would slow the train down if the engine weren't pulling... But as long as the train is moving at a constant speed the engine's pull is exactly balancing the friction and drag, thereby keeping the momentum constant.
 

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