What's the inertia of cart A?

In summary: From the graph you should be able to see that the mass of cart A is significantly greater than that of the standard cart. This shows the gap between your knowledge of the subject and the knowledge required to solve a problem like this.I'm really not sure I can help you through this...In summary, the conversation discusses the problem of calculating the inertia of cart A in a collision with a standard cart. The equation for moment of inertia, I=mr^2, is mentioned but the student is unsure how to use it. The concept of inertia is also discussed, with it being noted that it is usually used to refer to mass. The student attempts to use the equation F=ma, but realizes there are multiple unknown variables. The conversation
  • #36
emily081715 said:
what step have i missed? solving the rest of the equation i get an answer of 2.1 kg
I don't think you missed anything, and based on a visual inspection of the graph, that looks to be the correct answer. Why can I tell that with a visual inspection?
 
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  • #37
berkeman said:
I don't think you missed anything, and based on a visual inspection of the graph, that looks to be the correct answer. Why can I tell that with a visual inspection?
the answer should've been 2.50
 
  • #38
emily081715 said:
the answer should've been 2.50
Interesting. I could see maybe 2.2 if the estimate of v=4.2 should be v=4.4 instead, but to get all the way up to 2.5m/s would take something else.

Maybe we have to take the decreasing velocity due to friction into account. What is the full problem statement exactly?
 
  • #39
I estimated something like 2.55 to 2.7 kg .
 
  • #40
Hi emily081715!

Yes. We can see that the momentum of both carts decrease at a constant rate throughout.
So what's the total momentum before the collision, what's the momentum after the collision, and how much momentum did we lose during the collision?
 
  • #41
As a result of the collision, cart A lost momentum and the standard cart gained momentum. Can you look at the graph and determine how much less momentum cart A had as a result of the collision than it would have had if the collision had not taken place?
 
  • #42
Emily has other, more basic, problems that should be tackled before this one... get the basics down first.
Recommend anyone trying to help takes a look at past threads by this member first.
 
  • #43
Hi Simon Bridge,

I don't get what you mean.
Just from Emily's previous posts in this thread she seems the have a firm grasp on the total momentum, and on setting up equations and solving them.
The one thing missing is the loss due to friction - for which she did not get a clear response.
And her request to break it down went unanswered.
 
  • #44
I like Serena said:
Hi Simon Bridge,

I don't get what you mean.
Just from Emily's previous posts in this thread she seems the have a firm grasp on the total momentum, and on setting up equations and solving them.
The one thing missing is the loss due to friction - for which she did not get a clear response.
And her request to break it down went unanswered.
The problem apparently is that she re-posted this question after she did not get enough hand-holding in her first thread attempt, and I took the bait. The problem turned out to be more complicated than I expected when I first replied, which is fine, but it would have been good if I hadn't wasted so much time assuming it was a simple question when the OP knew already that it was not.

Thread closed.
 

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