4. Normal human body temperature is 310 K. (a) What is the peak wavelength emitted by a person with this temperature?
(b) What part of the spectrum does that wavelength lie in?
(c) If the surface area of a person is about 1.5 m2, what is their luminosity?
(d) How does that luminosity compare to a 100W(109erg s−1) light bulb?

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

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. but she does have devices to measure distance and time accurately. she knows her own mass is 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?

Newtons view of arrangement of the universe