Simple rolling friciton problem, where did I go wrong?

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In summary, the conversation is about calculating the distance a 50,000kg locomotive will roll before coming to a stop after its engine and brakes fail. The conversation also includes a discussion about the use of different coefficients for rolling friction and the realization that a locomotive has steel wheels on steel tracks. Ultimately, the person asking the question receives clarification and thanks the other person for their assistance.
  • #1
JBP_Ace
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Word for word:

A50,000kg locomotive is traveling at 10 m/s when its engine and breaks fail. How far will the locomotive roll before it comes to a stop?

Rolling friction for rubber on concrete is 0.02 (by the book)

a= fnet/m = (umg)/m so mass cancels out leaving a = ug = .02(-9.8) = -.196

I use Vf^2 = Vi^2 + 2ad (I'll just say d = distance in meters)
So it works out to
-100 = (-0.392)d
d = 255 m

but wait... the book says the answer's 2550!

I would figure that means the rolling friction is .002 but that's steel on steel (dry)

What am I doing wrong?
 
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  • #2
I'd assume you need the steel on steel coefficient. Don't locomotives with steel wheels run on steel tracks?

I don't see why you're using rubber and concrete.
 
  • #3
wow...

I read that and thought because it's a locomotive, then blood drained from my face.

a locomotive, a train... why the hell am I a physics major? lol

thanks! that's all I needed
 

Related to Simple rolling friciton problem, where did I go wrong?

1. Why does the object stop moving in a simple rolling friction problem?

The object stops moving because the force of friction acts in the opposite direction of the object's motion, causing it to slow down and eventually come to a stop.

2. Does the mass of the object affect the amount of friction in a simple rolling friction problem?

Yes, the mass of the object does affect the amount of friction. The greater the mass, the greater the force of friction, which means the object will slow down more quickly.

3. What is the difference between rolling friction and sliding friction?

Rolling friction occurs when an object rolls on a surface, while sliding friction occurs when an object slides on a surface. Rolling friction is typically less than sliding friction, making it easier for an object to keep rolling than to keep sliding.

4. How does the surface affect the amount of friction in a simple rolling friction problem?

The type of surface that the object is rolling on can greatly affect the amount of friction. A rough surface will create more friction, causing the object to slow down more quickly, while a smooth surface will create less friction, allowing the object to roll further.

5. Can the force of friction ever be completely eliminated in a simple rolling friction problem?

No, the force of friction cannot be completely eliminated in any situation. However, it can be reduced by using smoother surfaces or lubricants, which will decrease the amount of friction and allow the object to roll further without slowing down as quickly.

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