What are the main general features that make clusters of stars useful to astronomers? a. the stars are at the same distance from earth, were formed at approximately the same time, and were made from the same chemical mix. b. the stars all have the same intrinsic brightness but differ in size and surface temperature. c. the stars all have the same apparent magnitude, the same surface temperatures, and the same sizes. d. the stars are all at the same distance from earth, have the same surface temperature, and joined the cluster at various times.

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.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.

a=d/t

a="triangle"v/t

explanation:

a = acceleration