What is the equation to calculate speed?

The of a machine determines its "usefulness." a. input force b. output force c. mechanical advantage

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

Unpolarized light whose intensity is 1.19 w/ is incident on a polarizer. (a) what is the intensity of the light leaving the polarizer? (b) if the analyzer is set at an angle of = 41.0∘ with respect to the polarizer, what is the intensity of the light that reaches the photocell?