A man jumps from an airplane and does not open his parachute immediately. As he falls,
two forces act on him: the force mg due to
gravity and the force n, of air resistance. Now
he opens his parachute and begins to fall at
constant velocity.
What forces act upon him now?
1. Since he is falling at constant velocity
gravity no longer acts on him.
2. None of these
3. Since he is falling at constant velocity the
force of air resistance no longer acts on him.
4. The same two forces act on him as before;
the only change is that with the parachute
open, the two forces sum to zero.
5. When the parachute opens there is an
additional force n, which has nothing to do
with either n, or mg

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answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.

b mirrors submit a iisner? e. for which optical devices does d sometimes have a positive value? o a a and b o b. a and c o c. b and d 0 d. b and cb

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.