I want you to explain me how #1 and #2 is different from #3.

Instead of solving the problem, please explain it to me how it's done.

I understand the law of center of mass, in which if I'm at boat w/ a ball, every time I throw the ball in front, the boat will go backwards.

If so, why is that law not applied for the third example? I'm confused because I understand how momentum is conserved w/ no external force, but isn't there no external force for the first two problems as well?

Also, how is law of conversation of momentum applied for the first two problems?

Please explain all of this to me in a clear answer. Thank you!

1)

Question 17 (1 points) (525856) {Conservation of Momentum) Passengers on a cruise ship are eager to arrive at their next destination. They decide to try to speed the cruise ship up by gathering at the bow ( front) of the ship and running all at once toward the stern (back) of the ship. While they are running toward the stern, what happens to the forward speed of the cruise ship? I it's a little higher than beforeQ it's a little lower than before it's the same Question 19 (1 points) (101 188) {Conservation of Momentum} You nd yourself trapped at rest on a 10 square meter sheet of polished molecular-deposited diamond, a surface that can be considered frictionless. What is the easiest way to get out of this strange situation? I Take off one of your shoes and throw its Simply stand up and walk away. Crawl away since it is not possible to walk Question 20 (407726) {Conservation of Momentum} Consider yourself and the Earth as one system. When you jump up, what happens to the momentum of the system? Increase in the downward direction as you rise I Increase in the downward direction as you fall I Stay the samea Dissipate because of friction