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Question on torques. quick one.

  • #1
410
11

Homework Statement


Untitled 3.jpg


Homework Equations


ok, I thought that the torque from the mass 'm' would be equal to torque from mass 'M'

The Attempt at a Solution


I wrote down:

m * g * (d/4) = M * g * d

(m/4) = M

m = 4M

Thus, the ratio is 4M : 1 m, which gives answer 1.

However, the solutions say that the answer is 5.

Could anyone please weigh in, and thanks in advance for the help!
 

Answers and Replies

  • #2
billy_joule
Science Advisor
1,200
330
I agree with your answer.
 
  • #3
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
32,760
5,036
Thus, the ratio is 4M : 1 m
No, you have shown 4M=1m. Think of M and m as numbers there. What is M/m?
 
  • #4
410
11
ahh 1/4. Right, thanks!
 
  • #5
I have another method,
For the system to be in equilibrium the centre of mass should lie exactly on the pivot.

Assume the pivot to be at (0,0)
assume M to be at (d,0)
assume m to be at (-d/4 ,0)
Applying the formula of center of mass
x c.o.m. = (m(-d/4) +Md)/(m+M) = 0

Md = md/4
M:m=1:4
 
  • #6
410
11
That sir is an awesome and time-saving method! Thanks a lot!!! Everyone thanks!!
 

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