4. A worker exerts 140 N to push a 15 kg crate 20 meters across the floor. He then lifts the crate 2 meters up to a shelf.
a. How much work is done to push the crate across the floor?
b. What work was done to lift the crate up?
c. What was the total work done by the worker?

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.

answercollision;