Consider that an adult human has an average walking speed of about 5.63 km/hr and burns approximately 4.5 calories/minute. (1 cal = 4.184 kj) also, assume that this energy comes from the oxidation of foods, which is about 30% efficient. how much energy do you save by walking 1 km as opposed to driving a car that gets 30 miles/gal? (the density of octane is 703 kg/m3).

The density of a planet is 0.69 g/cm3 (density of water is 1.0 g/cm3). which of the following planets might this be? a. mercury b. venus c. saturn d. mars

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.

How many moles are in 43.9 l of oxygen