What is the % efficiency of this system ?

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The discussion revolves around calculating the efficiency of a system involving physics problems related to momentum, power, and energy dissipation. The first problem involves a collision between two fish, where the larger fish's post-collision velocity needs verification, with an initial calculation suggesting it moves backward at -4 m/s. The second problem focuses on a pulley system lifting a weight, requiring calculations for power input and output, as well as the system's efficiency. The third problem addresses an inelastic collision, emphasizing the need to determine the wreckage's velocity and the energy dissipated as heat. Participants remind that they cannot complete homework for others but provide guidance on using conservation principles for momentum and energy.
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These are some problems I am having difficulty with, the first problem I got an answer but I am unsure if it is correct and the others I have no clue. If you can step by step how to do them it would be greatly appericated.

A 12 kg. fish swimming at a velocity of 3 m/s swallows an absent-minded 4 kg fish swimming toward it at 10 m/s. What is the velocity, including direction (e.g., direction of larger fish or smaller fish), of the larger fish after lunch ?

I used m=mv and I got the answer to be -4m/s (big fish travels bacwards from its original postion) < I am not sure if this is correct if you can verify that would be awsome.

2) A pulley system is set up to lift boxes weighing 750 N from ground level to a position 6 meters high. A man pulls 30 meters of rope with a force of 200 N.

(b) If it takes the man 50 seconds to accomplish this task, (1) how much power is he putting in and (2) how much power is he getting out ?



(c) What is the % efficiency of this system ?



3) Consider the inelastic collision between two objects (A and B). Object A has a mass of 10 kg. and is moving at 12 m/s. Object B has a mass of 6 kg. and is moving at 8 m/s toward object A (Objects A and B are moving towards each other). How much energy is dissipated as heat ?

HINT: The velocity of the wreckage must first be determined. Then use the principle of conservation of energy.

To whom who ever does it I truly thank you. :redface:
 
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I need the answers by 10 minutes from now, please anyone help...
 
For number two, P = \frac{W}{t} and W= Fd. Can you go from here?
 
PhysicsNoob88 said:
I need the answers by 10 minutes from now, please anyone help...

the rules are that we don't do your homework for you.
 
For No. 1 first conserve momentum and then v = momentum/mass
 
For no.3
whether the collision is elastic or inelastic momentum is conserved.
The difference of initial and final energies is the heat dissipated.
 
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