The Mass is the fixed value. It doesn’t change by changing its shape ?

The center of mass doesn't move from one part of the raft to the other, but the raft moves from one side of the center of mass to the other. The raft is not fixed, from the perspective of the lake. As the boy's feet push himself forward, they also push the raft backward.

Explanation:

i take the test and it's correct

answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation:

he is very short, and he can only reach halfway up on the elevator buttons. but on a rainy day, he has his umbrella with him, and he uses it to poke the button at the top.