The driver of a 3000 lb. car, coasting down a hill, sees a red light at the bottom, and must stop. His speed when he applies the brakes is 60 mph, and he is 100 feet (vertically) above the bottom of the hill. (a)How much energy as heat must be dissipated by the brakes if we neglect wind resistance and other frictional effects

Explanation:

60 mph = 60 x 1760 x 3 / (60 x 60) ft /s

speed of car , v = 88 ft /s

kinetic energy of car = 1/2 m v²

= .5 x 3000 x 88²

= 11616 x 10³ poundal - foot

Potential energy = mgh

= 3000 x 32 x 100

=  9600 x 10³ poundal - foot

Total energy = potential energy + kinetic energy

= ( 11616 + 9600 )x 10³

= 21216 x 10³ poundal - foot .

This energy is dissipated as heat when brakes are applied on the car to stop the car .

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.

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