Okay i'm totally stuck and nobody i know really gets it either, so i've turned to yahoo for : )
basically there are four aliens on a planet. they want to go on a sea-saw. the end seats on the sea-saw are 2m from the pivot, and the middle seats are 1m from the pivot. the aliens way 400n, 300n, 200n and 100n - which two can sit on the sea-saw (on any of the seats) and make it balance? it'd be a huge if you at least me work out the answer! : )

Three different objects, all with different masses, are initially at rest at the bottom of a set of steps. each step is of uniform height . the mass of each object is a multiple of the base mass : object 1 has mass 4..00m , object 2 has mass 1..96m , and object 3 has mass . when the objects are at the bottom of the steps, define the total gravitational potential energy of the three-object system to be zero. if the objects are then relocated as shown, what is the new total potential energy of the system? each answer requires the numerical coefficient to an algebraic expression. each algebraic expression is given using some combination of the variables , , and , where is the acceleration due to gravity. enter only the numerical coefficient. (example: if the answer is 1..23mgd , just enter 1.23)

Why can blue light and yellow light combine to produce white light? question 17 options: they are both primary colors of light. they absorb each other's wavelengths. because blue, yellow, and white are primary colors. they are complementary colors of light.

How would a small bar magnet be oriented when placed at position x?