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the objective lens of the refracting telescope at the lick observatory in california has a focal length of 57 ft.
what is the refractive power of this lens?
what focal length (mm) eyepiece would give a magnification of 1000x for this telescope?

The desk has a weight of 75 lb and a center of gravity at g. determine the initial acceleration of a desk when the man applies enough force f to overcome the static friction at a and b. also, find the vertical reactions on each of the two legs at a and at b. the coefficients of static and kinetic friction at a and b are ms = 0.5 and mk = 0.2, respectively

What is relative velocity? in which condition is relative velocity known by adding the velocity of the first body and that of the second body

Which of the following is an example of units for speed