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A Squeezed Liquid Lifts a Whole Car

5th grade nonfiction passage about how a hydraulic jack works: 223 words, six questions, an answer key and vocabulary.

5th grade nonfiction how a hydraulic jack works 223 words

A Squeezed Liquid Lifts a Whole Car

Lifting a car by hand sounds impossible, yet a garage worker can do it with a small tool called a hydraulic jack. The secret is a liquid, usually oil, that cannot be squeezed into a smaller space.

A hydraulic jack has two cylinders joined by a tube. One cylinder is narrow, and the other is wide. Each has a piston, which is a plug that slides up and down. The oil fills the space between the pistons.

When the worker pumps a handle, the narrow piston pushes down on the oil. Because the oil cannot be squashed, the push travels through the liquid and presses up on the wide piston. A scientist named Blaise Pascal explained this idea long ago. Pressure in a closed liquid spreads out equally in every direction.

Here is why the jack is so strong. The wide piston has much more surface for the pressure to push against. A small force on the narrow piston becomes a large force on the wide one. That large force is strong enough to raise a heavy car.

There is a trade, as with many machines. The narrow piston must move down many times to lift the wide piston a small amount. The worker pumps the handle again and again, and the car rises slowly. Hydraulic machines also help dig, lift, and brake.

Questions

  1. What liquid is usually used inside a hydraulic jack? in the text

  2. How are the two cylinders of a jack connected? in the text

  3. What is a piston? in the text

  4. Who explained that pressure spreads equally in a closed liquid? in the text

  5. Why does a small push on the narrow piston lift a heavy car? think about it

  6. Why does the worker have to pump the handle many times? think about it

Words to know

hydraulic
worked by a liquid that is under pressure
piston
a plug that slides inside a cylinder
pressure
a pushing force spread over a surface
squash
to press something flat or smaller
surface
the outside area of something
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One passage, three levels

The same topic and facts written three ways, so a mixed class can read and talk about one text. Each group’s sheet shows only a shape; the key says which is which.

● Easier · 200 words · Flesch-Kincaid grade 3.1

A garage worker can lift a car with a small tool. It is called a hydraulic jack. The secret is a liquid, often oil. Oil cannot be squeezed into a smaller space.

A hydraulic jack has two cylinders joined by a tube. One cylinder is narrow. The other is wide. Each has a piston, a plug that slides up and down. Oil fills the space between them.

The worker pumps a handle. The narrow piston pushes down on the oil. The oil cannot be squashed. So the push goes through the oil and presses up on the wide piston. A scientist named Blaise Pascal explained this long ago. Pressure in a closed liquid spreads out the same in every direction.

Here is why the jack is strong. The wide piston has more surface for the pressure to push on. A small force on the narrow piston becomes a big force on the wide one. That big force can raise a heavy car.

There is a trade. The narrow piston must move many times to lift the wide piston a little. So the worker pumps again and again, and the car rises slowly. Hydraulic machines also help dig, lift, and brake.

▲ This passage · 223 words · Flesch-Kincaid grade 5.2

Lifting a car by hand sounds impossible, yet a garage worker can do it with a small tool called a hydraulic jack. The secret is a liquid, usually oil, that cannot be squeezed into a smaller space.

A hydraulic jack has two cylinders joined by a tube. One cylinder is narrow, and the other is wide. Each has a piston, which is a plug that slides up and down. The oil fills the space between the pistons.

When the worker pumps a handle, the narrow piston pushes down on the oil. Because the oil cannot be squashed, the push travels through the liquid and presses up on the wide piston. A scientist named Blaise Pascal explained this idea long ago. Pressure in a closed liquid spreads out equally in every direction.

Here is why the jack is so strong. The wide piston has much more surface for the pressure to push against. A small force on the narrow piston becomes a large force on the wide one. That large force is strong enough to raise a heavy car.

There is a trade, as with many machines. The narrow piston must move down many times to lift the wide piston a small amount. The worker pumps the handle again and again, and the car rises slowly. Hydraulic machines also help dig, lift, and brake.

■ Harder · 232 words · Flesch-Kincaid grade 7.5

Lifting a car by hand sounds utterly impossible, yet a garage worker can accomplish it with a modest tool called a hydraulic jack. The secret is a liquid, usually oil, which cannot be squeezed into a smaller space.

A hydraulic jack consists of two cylinders connected by a tube. One cylinder is narrow, while the other is wide. Each contains a piston, which is a plug that slides up and down, and oil fills the space between the two pistons.

When the worker pumps a handle, the narrow piston presses down on the oil. Because the oil cannot be compressed, the push travels through the liquid and presses upward on the wide piston. A scientist named Blaise Pascal explained this principle long ago: pressure in a closed liquid spreads out equally in every direction.

Here is why the jack is so powerful. The wide piston offers far more surface for the pressure to push against. A small force on the narrow piston is therefore transformed into a large force on the wide one, and that large force is strong enough to raise a heavy car.

As with many machines, there is a trade. The narrow piston must travel downward many times to lift the wide piston by a small amount. The worker pumps the handle again and again, and the car rises gradually. Hydraulic machines also assist with digging, lifting, and braking.

Download as one PDF

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put hydraulic, piston, pressure, squash and surface on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 2 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 5 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "A Squeezed Liquid Lifts a Whole Car"?

It was written for 5th grade. It has 223 words and works out to a Flesch-Kincaid grade level of about 5.2. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are six. 4 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 2 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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