How Far Must the 30 kg Child Sit for Seesaw Equilibrium?

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Homework Help Overview

The problem involves two children on a seesaw, where one child weighs 35 kg and is positioned 2.0 m from the pivot. The goal is to determine how far the 30 kg child must sit from the pivot for the seesaw to achieve equilibrium. The subject area includes concepts of moments and equilibrium in mechanics.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of moments and the conditions for equilibrium. Questions arise about the definitions of moments and the appropriate point to measure them from. There is uncertainty regarding the relevant equations and how to apply them to the problem.

Discussion Status

Some participants have offered guidance on calculating moments and have prompted the original poster to consider the forces acting on the seesaw. There is an ongoing exploration of how to set up the problem, with various interpretations of the necessary calculations being discussed.

Contextual Notes

Participants express a lack of familiarity with terms related to moments and equilibrium, indicating a need for clarification on fundamental concepts. The discussion includes attempts to convert weights into Newtons and to understand the relationship between mass, gravity, and distance from the pivot.

Fabio233
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Homework Statement


Two children are sitting on opposite ends of a uniform seesaw of negligible mass, if a 35 kg child is 2.0 m from the pivot point, how far from the pivot point will her 30 kg playmate have to sit on the other side for the seesaw to be in equilibrium. please help

Homework Equations



Im not sure what to use??

The Attempt at a Solution


Not sure, that's why i am here
 
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Do you know how to calculate a moment of a force? Do you know what the sum of the moments about a point must be equal to for there to be equilibrium?
 


im sorry I am not familiar to these terms, do you have an equation i can use
 


The moment of a force is the Force multiplied by the distance from the point of rotation. Where in the see-saw do you think is a good place to take moments about? (i.e. where is the best place to measure the rotation from?)
 


would it be the pivot point?
 


Fabio233 said:
would it be the pivot point?

Yes it would, so what are the forces acting and what distances are they from the pivot point?
 


would the forces be mass and gravity and, distance 2m from pivot point
 


Fabio233 said:
would the forces be mass and gravity and, distance 2m from pivot point

Mass and gravity is the weight of the people.

So let's call the distance of the 30kg child from the pivot point d. So what is the child's moment about the pivot point?

Similarly what is the moment of the 35kg child about the pivot point?
 


oh so i take 35/2=17.5
30/4=7.5
17.5/7.5=2.3m
 
  • #10


Fabio233 said:
oh so i take 35/2=17.5
30/4=7.5
17.5/7.5=2.3m

No 35kg is how many Newtons if g=9.81 N/kg? Convert 30kg to N as well.

The moment of child 1 about pivot = Child's weight*distance from pivot.
 

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