If a car generates 20 hp when traveling at a steady 70 km/h , what must be the average force exerted on the car due to friction and air resistance? Express your answer to two significant figures and include the appropriate units.

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