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

In summary, 4 bob sledders are applying 25N each for the first 3 seconds with an empty sled, then one jumps in, leaving 3 of them pushing with 25 N each for 1 second etc… am I interpreting this correct? I think we need the sledders masses to find the velocity at the end?
  • #36
paulimerci said:
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.
 
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  • #37
paulimerci said:
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
erobz said:
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.
 
  • #38
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.
 
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  • #39
erobz said:
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.
 
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