science

Puretic power block

Puretic power block is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Puretic power block rather than just read about it. In short: The Puretic power block is a special kind of mechanised winch used to haul nets on fishing vessels. The power block is a large pulley of aluminium with a hard rubber-coated sheave.

Key takeaways

Puretic power block belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Puretic power block to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Puretic power block from memory before moving on to harder problems.

Reference excerpt

The Puretic power block is a special kind of mechanised winch used to haul nets on fishing vessels. The power block is a large pulley of aluminium with a hard rubber-coated sheave. While many men were needed for the back-breaking work of hauling a purse seine manually, the same work could be done by fewer men with a power block. The Puretic power block revolutionized the technology of hauling fishing nets, particularly purse seine nets. According to the Food and Agriculture Organization of the United Nations (FAO), "no single invention has contributed more to the success of purse seine net hauling" than the power block, which was "the linch-pin in the mechanization of purse seining".

History The power block was invented by a Croatian fisherman, Mario Puratić, and patented in 1953. In English, Puratić is usually incorrectly spelt Puretic, sometimes Puretich. While he was working as a tuna and sardine fisherman from San Pedro, California, Puratić started thinking about the difficulty of hauling seine nets. The original power block he designed was essentially a simple winch which used a V-shaped roller coated with hard rubber. It was suspended from a davit, and powered from the warp end of the winch by a looping rope. In 1954, the power block was trialled by American purse seiners in the Pacific. They have evolved since then, and nowadays power blocks are powered by hydraulic pumps. Their speed, torque and direction can be remotely controlled from the bridge during operations. As a result, retrieving the net is safer and requires less manual work. Other important innovations of the same period were the development of synthetic fishing nets and sonar detection devices. The combination of the automated power block hauling synthetic nets with sonar sensing revolutionised the industry.

The use of power blocks was found to have further advantages. It is possible to fish in rougher weather with the power block, because the steady force exerted by the net stabilizes the vessel. When deployments are made which miss the schooling fish, the net can be rapidly retrieved and redeployed on the same school. The power block also makes it easy to get nets aboard in emergencies, such as a sudden shift in tides or winds, or shark attacks on the catch and net. On the other hand, the increase in the effectiveness of purse seine fishing led to herring schools choosing to school deeper in the water. Nets that could operate in deeper water needed to be bigger and heavier. That in turn meant bigger vessels, which pushed the smaller herring vessels out of business.

Economic effects Seine fishing industries rapidly recognized the value of the power block, and by 1960, most northern seine vessels were using the power block. Nowadays power blocks come with dozens of configurations and sizes. They are installed on over twenty thousand fishing vessels across the major purse seining fisheries around the world. These fisheries haul huge schools of tuna, salmon, herring, sardines, anchovies and menhaden from the sea, accounting for a large part the world's total fish catch. Between 1969 and 1979, the Puretic power block was pictured on the reverse side of Canadian five dollar banknote issues. In 1975 Mario Puratić was given the National Inventor of the Year Award by the Intellectual Property Owners Education Foundation for his invention of the power block. A 2022 paper claims the reduction in labour demand resulting from use of the power block means power blocks devalue black labour on white owned ships.

References

Illustrations

Worked examples

Example 1 — a first encounter with Puretic power block

Start with the simplest possible case. Write down what Puretic power block claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Puretic power block before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Puretic power block ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Puretic power block

In research: Puretic power block appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Puretic power block in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Puretic power block is common in secondary-school and first-year university syllabi. It links to neighbouring topics Croatian inventions, Fishing equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Puretic power block outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Puretic power block in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Puretic power block means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Puretic power block out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Puretic power block in simple terms?

The Puretic power block is a special kind of mechanised winch used to haul nets on fishing vessels. The power block is a large pulley of aluminium with a hard rubber-coated sheave.

Why does Puretic power block matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Puretic power block?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Puretic power block.