Need help with a seesaw torque question.

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    Seesaw Torque
AI Thread Summary
Halle and Susan, each weighing 40 kg, are on opposite ends of a 4.50 m seesaw, which is initially stationary. When Susan jumps off, the unbalanced torque acting on the seesaw needs to be calculated. The force exerted by Susan is determined to be 392 N, calculated using F=ma. The distance from the pivot to Susan's position is assumed to be half the length of the seesaw, or 2.25 m. This information is crucial for calculating the torque and understanding the seesaw's dynamics.
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Homework Statement


Halle and Susan, each of mass 40 kg are sitting at opposite ends of a playground seesaw. The seesaw is stationary in the horizontal position and is 4.50 m long. Susan decides to jump off. Calculate the size of the unbalanced torque that now acts on the seesaw.


Homework Equations


torque= F * r (perpendicular distance?)
F=ma


The Attempt at a Solution


I'm not sure how to find the perpendicular distance from the line of action of the force to the axis of rotation. I think F would be 40*9.8=392 N but I don't know how to find the "r" value.
 
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paperdoll said:
I'm not sure how to find the perpendicular distance from the line of action of the force to the axis of rotation. I think F would be 40*9.8=392 N but I don't know how to find the "r" value.
How far is she from the pivot of the seesaw? (You're given the full length of the seesaw.)
 
Doc Al said:
How far is she from the pivot of the seesaw? (You're given the full length of the seesaw.)

It doesn't state the value in the question so I guess you are supposed to assume that she is half way. So 4.5/2=2.25 m
 
paperdoll said:
It doesn't state the value in the question so I guess you are supposed to assume that she is half way. So 4.5/2=2.25 m
Yes, that's what I would assume. The axis of the seesaw is in the middle and she is sitting at one end.
 
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