Balancing Teeet Totter: Lever Arm Calculation

• alex7298
In summary, the conversation is about finding the correct placement of the fulcrum on a "teeter totter" playground equipment to balance two children with different masses. The person asking for help has attempted a solution using the equation T=0 and setting up an equation for the resultant torque. However, they are struggling to find the correct answer and have asked for clarification. The conversation also briefly mentions the assumption that the "teeter totter" is massless.
alex7298
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Homework Statement

Two children whose masses are 35kg and 55kg are on a playground "teeet totter" which is 3.0m long. Where must the fulcrum be placed so that the children will balance?
(35kg on left, 55kg on right)

sum of T=0

The Attempt at a Solution

I started with T=0=F(left)L(left)-F(right)L(right)
The two lever arms must add to be 3.0m so L(left)=3.0m-L(right). Through some algebra i got the equation into terms of L(right):
L(right)=(3m)(Fleft)/(2(Fright))
I get the right lever to be .95m, but is supposed to be between 1-1.5

Where am i going wrong??
Thanks

Anyone??

Start simple.

Let the distance from one end be x metres, then the distance from the fulcrum to the other end is (3-x)metres.

For it to be balances the resultant torque about the fulcrum must be zero.
Can you set up the equation now?

This is all assuming the teeter totter is massless.

Last edited:
teacher said you can ignore mass of teeter totter.
And to rock.freak667, that's exactly how i started. I got 0=(x-3)(Fleft)-(X)(Fright)...

Clockwise moment about pivot=(33gx) Nm
Anti-clockwise moment about pivot=55g(3-x) Nm

For balance

55g(3-x)=33gx

Are you sure you did the algebra correctly?

55(3-x)=33x
165-55x=33x
88x=165

r*m = r*m

1. What is a lever arm?

A lever arm is the distance between the fulcrum (pivot point) and the point where the force is applied. It is a crucial factor in calculating the balance of a teeter totter.

2. How do you calculate the lever arm?

The lever arm can be calculated by measuring the distance from the fulcrum to the point where the force is applied. In most cases, this distance is measured in meters or feet.

3. Why is it important to calculate the lever arm?

Calculating the lever arm is important because it determines the balance of a teeter totter. If the lever arms on both sides are equal, the teeter totter will be balanced. However, if one side has a longer lever arm, it will have more leverage and cause the teeter totter to tip towards that side.

4. What other factors affect the balance of a teeter totter?

In addition to the lever arm, the weight and distance of the objects on each side of the teeter totter also affect its balance. The heavier the object, the more force it exerts, and the further it is from the fulcrum, the greater its leverage.

5. How can I ensure that my teeter totter is balanced?

To balance a teeter totter, you must ensure that the lever arms on both sides are equal. This can be achieved by adjusting the weight or distance of the objects on each side. You can also use the lever arm calculation to determine the necessary adjustments for balance.

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