What is meant by the term friction?

In a given chemical reaction, the energy of the products is greater than the energy of the reactants. which statement is true for this reaction?

With the simplified model of the eye, what corrective lens (specified by focal length as measured in air) would be needed to enable a person underwater to focus an infinitely distant object? (be careful-the focal length of a lens underwater is not the same as in air! assume that the corrective lens has a refractive index of 1.62 and that the lens is used in eyeglasses, not goggles, so there is water on both sides of the lens. assume that the eyeglasses are 1.90

Notice how they put future which of the clouds shown would indicate a possible future rain storm? a) b) c) d)