BR Physics 4.6a Math Error?

[ipodtouch]

Wow, I think I just caught BR in some serious math error.

The problem deals with fulcrums. The solution shows 2 methods for solving this problem.
The math in the following 2 solutions go as:

#1
(250)X-(300)(6-x)=0
250X-1800+300X=0
x=3.3

#2
(550)X-(300)(6-x)=0
550X-1800=0
x=3.3

Look at #2, what? They completely left out an X component.
It should say
(550)X-(300)(6-x)=0
550X-1800+300X=0
X=2.12




I was laboring over this because I couldn't see at all how method #2 could be true. And the math seems to show that it's not possible.
Is there anything that I am overlooking?

What is the "proper" method #2 for solving this problem?



Thanks~

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[saoj]

What is the section, passage number and question number? Usually just the section and question number suffice...

 

[MedPR]

What is the section, passage number and question number? Usually just the section and question number suffice...

BR Physics 4.6a Math Error?

👍

 

[saoj]

👍

My bad, this is an example, not a passage/question.

 

[MedPR]

Pretty sure the (6-X) term in #2 should just be 6. If you set your torque point to be the 250N weight, that means that the 350N weight is 6m away from the torque point, not (6-X).

 

[ipodtouch]

Pretty sure the (6-X) term in #2 should just be 6. If you set your torque point to be the 250N weight, that means that the 350N weight is 6m away from the torque point, not (6-X).

Yeah you're definitely right. I was trying to visualize as to the math in the book with the lighter weight as the fulcrum, and it seemed impossible.

Thanks!