A sunbather is lying on a floating raft that is staionary. She then gets up and walks to one end of the raft. Consider the sunbather and raft as an isolated system. (a) What is the velocity of the center of mass of this system while she is walking? (b) Does the raft itself move while she is walking? If so, what is the direction of the raft's velocity relative to that of the sunbather?

Explanation:

It is given that initially sunbather and girl is at rest on the raft i.e. Center of mass of the system is at rest.

When the girl starts walking on the raft then also the center of mass velocity will remain at rest as there is no external force acting on the system.

(b)So when the girl starts walking she pushes the boat in the opposite direction to move forward. Thus the direction of motion of the boat is in the opposite direction of motion of the girl.  

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.

c) up

hope this