Find the placement for 4th mass

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SUMMARY

The discussion focuses on determining the placement of a fourth mass on a meter stick to achieve balance, given three existing masses located at 25 cm, 45 cm, and 90 cm. The relevant equation for this problem is the torque equation, T = r × F, and the balance condition m1r1 + m2r2 + m3r3 = m4r4. Participants emphasize that since all masses are identical, they can be treated as an unknown variable, simplifying the calculations. The key takeaway is that the placement of the fourth mass can be calculated by ensuring the torques on either side of the fulcrum are equal.

PREREQUISITES
  • Understanding of torque and its calculation using T = r × F
  • Familiarity with the concept of moments and balance in physics
  • Ability to set up and solve equations involving multiple variables
  • Knowledge of the properties of identical masses in equilibrium situations
NEXT STEPS
  • Study the principles of static equilibrium in physics
  • Learn how to apply the torque equation in various scenarios
  • Explore problems involving multiple masses and their placement for balance
  • Investigate the concept of center of mass and its application in balancing systems
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the principles of balance and torque in static systems.

leighkla
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Homework Statement


a meter stick is initially balanced on a fulcrum at its midpoint. you have four identical masses. three of them are placed at the following locations: 25 cm, 45 cm, and 90 cm. where should the fourth mass be placed in order to balance the meter stick?

Homework Equations


T=rxF ; m1r1+m2r2=m3r3=m4r4
each mass is identical but the problem does not give a mass.

The Attempt at a Solution

 
Last edited:
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Please fill in the template. List any equations/principles you have been taught which you suspect are relevant and show your thinking so far.
 
leighkla said:
each mass is identical but the problem does not give a mass.
Don't let that stop you. Just fill in the masses as an unknown m and trust that if there is no mistake in the question then m will disappear later.
leighkla said:
m1r1+m2r2=m3r3=m4r4
Is there a typo in there?
What values for r1, etc. should you plug in?
 

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