Question

I am struggling on this physics question. Could someone please give me the answer to it with a detailed explanation? Thanks in advance ​

Question is in the image

Answer 1

The new velocity of the big fish is 2.00m/s since the mass and velocity of the small fish doesnt affect the big fish in any way

Answer 2

Let the big fish’s direction be positive:
m(1)v(1)+m(2)v(2)=m(12)+v(12)

(9.90)(2.00)+(0.10)(-4.00)=(9.90+0.10)v(f)
v(f)=1.94m/s[same direction as big fish]

I believe this is a conservation of momentum question. Because (momentum=mass•velocity), the system, if momentum is conserved, will be (mass of big fish•velocity of big fish+mass of small fish•velocity of small fish=mass of both fish combined+velocity of both fish combined). You add the masses because they are now both travelling as 1 mass. Same with final velocity, they are both one mass so they have to travel together at the same velocity.