On august 10, 1972, a large meteorite skipped across the atmosphere above the western united states and western canada, much like a stone skipped across water. the accompanying fireball was so bright that it could be seen in the daytime sky and was brighter than the usual meteorite trail. the meteorite's mass was about 4.4 × 106 kg; it's speed was about 14 km/s. had it entered the atmosphere vertically, it would have hit earth's surface with about the same speed. (a) calculate the meteorite's loss of energy (as a positive number, in joules) that would have been associated with the vertical impact. (b) express the energy as a multiple of the explosive energy of 1 megaton of tnt, which is 4.2 × 1015 j. (c) the energy associated with the atomic bomb explosion over hiroshima was equivalent to 13 kilotons of tnt. to how many hiroshima bombs would the meteorite impact have been equivalent?

(a)

The energy lost by the meteorite is equal to its initial kinetic energy, since the meteorite comes to a stop, therefore it loses all its energy:

where

is the mass of the meteorite

is the meteorite's speed

Substituting into the formula, we find

(b) 0.1 Megaton

1 Megaton (MT) corresponds to:

So, we can find how many MT the energy of the meteorite corresponds to by using the following proportion:

Solving for x we find:

(c) 7.9 Hiroshima bombs

1 kiloton (kT) corresponds to 1/1000 of megaton, so:

As before, we can find how many kiloton the energy of the meteorite corresponds to by using the following proportion:

Solving for x we find:

The energy of the Hiroshima bomb was 13 kiloton, so the impact of the meteorite corresponds to:

so, to 7.9 Hiroshima bombs.

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.