Hi everyone,(adsbygoogle = window.adsbygoogle || []).push({});

This is not really a homework question per se since it's not an assignment. Basically, our physics professor gave us a 100+ page syllabus filled with example questions and solutions and I am practicing with them by doing them one after the other. This one question I'm having trouble with. Here it is:

The first thing that pops into my mind is that the rod is 1 meter long, and according to the professor's solution point P must be 1.25 meters from the end of the rod. However, in the drawing, the point P is actually on the rod. It seems a bit unintuitive to me that the force would be acting outside of the rod?

For the position of the resultant, my calculations are like this if x is the distance between points P and O:

(10 kg)(x) - (15 kg)(0.5 - x) - (5 kg)(1 - x) = 0

(10 kg)(x) - 7.5 kg + (15 kg)(x) - (5 kg) + (5 kg)(x) = 0

x (10 kg + 15 kg + 5 kg) = 7.5 kg + 5 kg

x (30 kg) = 12.5 kg

x = 12.5 kg / 30 kg = 0.42

I'm not sure what I'm doing wrong? I think the solution has all the forces as a negative when he's adding them up, but shouldn't the 10 kg force be a different sign than the 15 kg and the 5 kg one?

Thanks for any help

(Note: I ticked the box saying that I used the template, but I don't think it applies for this question since it's not really an assignment, it's just a question with the solution and I need help understanding the solution. I hope it's ok)

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Equilibrium with moments of forces

Have something to add?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**