Jupiter subtends an angle of 1.67 10-4 rad when viewed by the unaided eye and 3.20 10-2 rad when viewed through an astronomical telescope that has a 0.043-m focal length eyepiece. Determine the focal length of the telescope's objective lens.

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

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force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach