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: option c. i.e. electric current flowing “downhill” from the negative electrode to the positive electrode in a battery

explanation:

the water analogy to the circuits define the pipes (water flows) to the electric current. now, we know that the electric current flows from the positive terminal to the circuit (as shown in the diagram attached).

hence, option c is the correct answer.

b. latent learning (the word "latent" itself means something that exists but isn't obvious, only under certain conditions! )