Find the final velocity of the bobsled after the last bobsledder jumps in

[erobz]

Not to me. Either 1000Ns is wrong or the problem statement is wrong.

Yeah, the problem statement doesn’t match the solution. But what at @paulimerci did in #10 given the circumstances is a reasonable approach…that’s what’s important IMO.

@palimerci please feel free to complain to the instructor about the better interpretation not jiving with the solution. The impulse should be 450 [Ns] IMHO. I assume @haruspex agrees?

 

[paulimerci]

Yeah, the problem statement doesn’t match the solution. But what at @paulimerci did in #10 given the circumstances is a reasonable approach…that’s what’s important IMO.

@palimerci please feel free to complain to the instructor about the better interpretation not jiving with the solution. The impulse should be 450 [Ns] IMHO.

 

[paulimerci]

Thank you, @erobz. It appears that I provided a reasonable interpretation this time.

Sure, will do!

 

[erobz]

Thank you, @erobz. It appears that I provided a reasonable interpretation this time.

You see what is being said right? To get the answer they want, it doesn’t align with the wording of the OP. It’s like they were saying the second guy pushes for 6 more seconds than the first, etc… when they actually said the second guy pushes for 6 seconds…The 1000 [Ns] impulse is the result of a very poor/completely wrong interpretation.

 

[paulimerci]

You see what is being said right? To get the answer they want, it doesn’t align with the wording of the OP. It’s like they were saying the second guy pushes for 6 more seconds than the first, etc… when they actually said the second guy pushes for 6 seconds…The 1000 [Ns] impulse is the result of a very poor/completely wrong interpretation.

I see that the question is poorly stated. Is it wrong for the second guy to push longer than the first? The time taken by each sledder can be different, right? I understand the answers doesn't make sense.

 

[erobz]

I see that the question is poorly stated. Is it wrong for the second guy to push longer than the first? The time taken by each sledder can be different, right? I understand the answers doesn't make sense.

I wouldn’t say is wrong that they push longer, but how much longer is a stretch.

Physiologically, the last guy is outputting some pretty high wattage, for a pretty long time, not to mention how much distance they cover before getting into the sled…the real guys are in under 5 seconds (total elapsed time).

The real problem here is the solution does not match the problem statement.

 

[paulimerci]

I see that the question is poorly stated. Is it wrong for the second guy to push longer than the first? The time taken by each sledder can be different, right? I understand the answers

I wouldn’t say is wrong that they push longer, but how much longer is a stretch.

Physiologically, the last guy is outputting some pretty high wattage, for a pretty long time, not to mention how much distance they cover before getting into the sled…the real guys are in under 5 seconds (total elapsed time).

The real problem here is the solution does not match the problem statement.

I don't know why teachers create such difficult problems; they are unrealistic, to be sure. I'm happy that you and @haruspex were able to identify the problem within the problem.

 

[erobz]

I guess they are just trying to keep it interesting, and someone (may not have been the instructor) didn't give it the thought it deserved.

I'm not an academic, but I don't see the prof. solving every problem they pull from a new textbook. They probably let statistics sort it out...enough people bring up an issue, they give it a check.

 

[paulimerci]

I guess they are just trying to keep it interesting, and someone (may not have been the instructor) didn't give it the thought it deserved.

I'm not an academic, but I don't see the prof. solving every problem they pull from a new textbook. They probably let statistics sort it out...enough people bring up an issue, they give it a check.

I guess so. It's really odd. The problem statement for a different question I posed in the forum yesterday was also discovered to be incorrect. Thanks to @jbriggs444 who gave a detailed explanation of what's wrong with the question and how it is inconsistent with the answer sheet provided. Thank you very much, Erobz and Haruspex. I'm learning a lot in this forum.