Question

Plz help meh and explain how to do it i suck at physics...

Answer 1

The variables with the subscript "i" refer to the initial masses (m) and velocities (v) of the shark and fish.

`m_(1,i)` = 10 kg

`m_(2,i)` = 0.5 kg

`v_(1,i)` = 5 m/s

`v_(2,i)` = 0 m/s

The variables with "f" refer to the final masses and velocities. Use the law of conservation of momentum to calculate these. The law says that the total momentum of the shark and fish before the fish is eaten should be equal to the momentum after the fish is eaten. We have

`m_1v_1` = (10 kg) (5 m/s) = 50 kg • m/s

`m_2v_2` = (0.5 kg) (0 m/s) = 0 kg • m/s

so the total momentum before the fish gets eaten is 50 kg • m/s.

When the shark eats the fish, its mass increases by 0.5 kg. So

`m_(1,f)v_(1,f)` = (10.5 kg)
`v_(1,f)` = 50 kg • m/s

Solve for
`v_(1,f)` by dividing both sides by 50.5 kg to get

`v_(1,f)` = (50 kg • m/s) / (50.5 kg) ≈ 4.76 m/s