What is meant by the term useful work done by a machine?

Use the data provided to calculate the gravitational potential energy of each cylinder mass. round your answers to the nearest tenth. 3 kg: kj 6 kg: kj 9 kg: kj

Unpolarized light of intensity i_0=750w/m^2 is incident upon two polarizers. after passing through both polarizers the intensity is i_2=280w/m^2. (a) what is the intensity of the light after it passes through the first polarizer in w/m^2? (b) write an equation for the angle between the polarizers in terms of the initial (i_0) and final (i_2) intensities. (c) find the angle between the polarizers in degrees.

How will the system respond to a temperature increase?