Question

A 20 kg fish swimming at 2 m/s swallows a 5 kg fish at rest. What is the speed of the large fish after lunch

Answer 1

1.6m/s

Step-by-step explanation:

Given parameters:

Mass of the big fish = 20kg

Mass of small fish = 5kg

Speed of big fish = 2m/s

Speed of small fish = 0m/s

Unknown:

Speed of the large fish after lunch = ?

Solution:

The momentum of the big fish before and after feeding is conserved.

Initial momentum = Final momentum

m₁v₁ + m₂v₂ = v (m₁ + m₂)

m₁ is mass of the big fish

v₁ is the speed of the big fish

m₂ is mass of the small fish

v₂ is the speed of the big fish

v is the final speed

Now insert the parameters and solve;

20 x 2 + 5(0) = v(20 + 5)

40 = 25v

v =
`(40)/(25)` = 1.6m/s