Answer: 3 m.
Explanation:
Neglecting the mass of the seesaw, in order the seesaw to be balanced, the sum of the torques created by gravity acting on both children must be 0.
As we are asked to locate Jack at some distance from the fulcrum, we can take torques regarding the fulcrum, which is located at just in the middle of the length of the seesaw.
If we choose the counterclockwise direction as positive, we can write the torque equation as follows (assuming that Jill sits at the left end of the seesaw):
mJill* 5m -mJack* d = 0
60 kg*5 m -100 kg* d =0
Solving for d:
d = 3 m.
To solve this problem it is necessary to apply the concepts related to the law of Malus which describe the intensity of light passing through a polarizer. Mathematically this law can be described as:

Where,
Indicates the intensity of the light before passing through the polarizer
I = Resulting intensity
= Indicates the angle between the axis of the analyzer and the polarization axis of the incident light
From the law of Malus when the light passes at a vertical angle through the first polarizer its intensity is reduced by half therefore

In the case of the second polarizer the angle is directly 60 degrees therefore



In the case of the third polarizer, the angle is reflected on the perpendicular, therefore, its angle of index would be

Then,



Then the intensity at the end of the polarized lenses will be equivalent to 0.09375 of the initial intensity.
Speed =distance over time