Torque is rotational mechanical force. Screws, bolts, engines, electric motors, flywheels, fans, and propellers all turn or rotate. The amount of force applied at a point on a rotating object, multiplied by the distance from the point of rotation determines the amount of torque. Torque forces are classified as causing either clockwise (cw) or counterclockwise (ccw) , sometimes called anticlockwise, rotation, determined by observing the rotation of the object as it faces you.
Torque = Force · Length of lever arm
“Length of lever arm” is a way of saying the distance between where the force is applied and the point of rotation. In order to tighten or loosen a bolt, you have to exert a torque on it. Using a wrench, the torque applied is equal to the amount of force used to pull the wrench multiplied by the distance between your hand and the center of the bolt. If you’ve ever used a wrench you probably know that it’s easier to tighten a bolt when holding the wrench at its end and harder to pull when you move your hand closer to the bolt. This is because the further your hand is from the bolt, the longer the lever arm, and the larger the torque.
We know that the torque you exert must be equal to 600 ft lbs [813.1 N m] and we know your weight, so we can plug those values into the torque formula and calculate the length of the lever arm.
Since you weigh less than your friend, you must sit further away from the see-saw’s point of rotation in order to produce the same torque as your friend. This will keep the see-saw balanced.