4. the density and strength of concrete are determined by the ratio of cement and aggregate. suppose that a contractor has 480 cubic feet of a dry concrete mixture that is 70% sand by volume. how much pure sand must be added to form a new mixture that is 75% sand by volume?

Write maxwell's equations and discuss the terms involved and the results of each equation in classical electrodynamics. if it is possible to write these equations in integral form, give the integral forms. find the wave equation for electromagnetic waves from the maxwell equations. what is the propagation velocity of electromagnetic waves in space according to the wave equation you find?

Density of salty water as compared to the density of pure water is(a) is less(b) is always equal(c) is always more(d) may be less or more

High schoolphysics 5+3 pts a neon light consists of a glass tube with metal wires at each end. when connected to a high-voltage source, the gas glows. if a fly lands on the glass tube, what will most likely happen? a) the fly will not feel a shock because the glass conducts any free electrons back into the gas. b) electrons will flow directly from the metal wires along the glass and shock the fly. c) the fly will not feel a shock because the glass insulates it from the electrons in the gas and the metal. d) electrons that are moving through the gas will be conducted through the glass and shock the fly.