Teeter Totter Balance: Why Does the Lighter Person's End Go Down?

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When a heavy person and a lighter person move toward the fulcrum on a teeter-totter, the lighter person's end goes down due to the principles of torque and balance. The force exerted by each person is determined by their weight and distance from the fulcrum, represented by the equation m1*d1=m2*d2. As they move closer to the fulcrum, the torque changes, and the side with the greater torque will rise. In the example discussed, if both individuals move in by one foot, the heavier person's side will exert more force, causing the lighter person's end to descend. Understanding these concepts is crucial for grasping the mechanics of balance on a seesaw.
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Homework Statement



suppose that a heavy person and a light person are balanced on a teeter totter made of plank wood. each person moves toward the fulcrum 25cm. why will the lighter persons end go down??

Homework Equations




not needed

The Attempt at a Solution


something about forces and gravity??
 
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Do you know the math to write the balancing equation for the two sides of the seesaw?
 
phinds said:
Do you know the math to write the balancing equation for the two sides of the seesaw?

math? i don't think so.
 
OK, I'm a bit puzzled as to how you can be working on such a simple problem and not know the math. What grade are you in?
 
phinds said:
OK, I'm a bit puzzled as to how you can be working on such a simple problem and not know the math. What grade are you in?

im a senior. i don't understand why we need math. were not finding a number.
 
physicsgurl12 said:
im a senior. i don't understand why we need math. were not finding a number.

No, you're not trying to get a number, you're trying to get an ANSWER, and the quantitative asnwer is a number and if you don't understand how to get the quantitative answer, you don't understand the answer.

Do you have no idea how a fulcrum works mathematically?
 
um not really. its like the piviot point. that's about all i know
 
If you had a seesaw with a 100 pound kid sitting out 10 feet from the center (the fulcrum), how much effort do you think it would be to keep him in the air if you could put your hand on the (strong, but weightless) seesaw a mile out on the other end?

How about 100 feet out?

How about 1 foot out?

What does thinking about this tell you?
 
that the amount of force depends on the distance
 
  • #10
good. Can you quantify that?
 
  • #11
umm i can try.
m1*d1=m2*d2
 
  • #12
excellent.

SO ... if we have, for example, a 100lb kid 10 feet out and a 200 lb man 5 feet out, then they balance, according to your equation (which is correct).

Now do the math if they both move in 1 foot.
 
  • #13
900 =600
 
  • #14
well, actually they are NOT equal, are they? So what does it mean in terms of who goes up and who goes down?

What do those numbers represent?

[by the way, check your math]
 
  • #15
sorry 800 haha. those number represent the force? It means the fat kid would go down?
 
  • #16
physicsgurl12 said:
sorry 800 haha. those number represent the force? It means the fat kid would go down?

Yes it represents force. Which side is exerting the most force? Does the most force cause the side that has it to go up or does the OTHER side go up?
 
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