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Why Water Stays in a Spinning Salad Spinner

8th grade nonfiction passage about inertia and circular motion: 258 words, six questions, an answer key and vocabulary.

8th grade nonfiction inertia and circular motion 258 words

Why Water Stays in a Spinning Salad Spinner

A salad spinner looks like a plain kitchen tool, but it is a neat lesson in motion. When you wash lettuce, drops of water cling to the leaves, but if you put the lettuce in the basket and spin it fast, the water leaves and gathers in the outer bowl. What pulls the water away? In truth, nothing does, and understanding the reason takes a close look at inertia.

Inertia is the tendency of an object to keep doing what it is already doing. A moving object keeps going in a straight line at the same speed unless some force changes its motion. A drop of water on a leaf is no different. When the basket spins, the drop wants to go straight ahead, which at any moment points along the edge of the circle rather than around it.

To make something travel in a circle, a force must keep pulling or pushing it toward the center. The basket can supply this force for the lettuce, because the leaves are held inside it, but the water is only loosely stuck to them, and the sticking is not strong enough to pull the drops around the curve, so the drops escape in straight lines and pass through the holes in the basket.

The same rule explains why a car passenger seems to slide toward the outside of a turn. The car turns, and the passenger's body tries to keep going straight until the door or seat belt pushes inward. Nothing flings the passenger outward. The body simply obeys inertia.

Questions

  1. Where does the water gather when the salad spinner turns fast? in the text

  2. What is inertia? in the text

  3. In which direction does a drop of water want to move when the basket spins? in the text

  4. Why do the leaves stay in the basket while the water leaves? think about it

  5. What must happen to make an object travel in a circle? in the text

  6. Why does a passenger seem to slide toward the outside of a turn? think about it

Words to know

inertia
the tendency of an object to keep moving or keep still
force
a push or a pull
curve
a smooth bend that is not a straight line
basket
a container with holes in its sides
obeys
follows a rule
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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 · 239 words · Flesch-Kincaid grade 4.1

A salad spinner looks like a plain kitchen tool. But it teaches a lot about motion. When you wash lettuce, drops cling to the leaves. Put the lettuce in the basket and spin it fast. The water leaves the leaves and gathers in the outer bowl. What pulls the water away? In truth, nothing does. To see why, we look at inertia.

Inertia is the tendency of an object to keep doing what it is already doing. A moving object keeps going in a straight line at the same speed unless a force changes its motion. A drop of water on a leaf is the same. When the basket spins, the drop wants to go straight ahead. At each moment, straight ahead points along the edge of the circle, not around it.

To make something move in a circle, a force must keep pulling or pushing it toward the center. The basket holds the leaves, so they go around. The water is only loosely stuck to them. The sticking is not strong enough to pull the drops around the curve. The drops fly off in straight lines through the holes in the basket.

The same rule explains why a car passenger seems to slide toward the outside of a turn. The car turns, but the passenger's body tries to go straight. Then the door or seat belt pushes inward. Nothing flings the passenger outward. The body just follows inertia.

▲ This passage · 258 words · Flesch-Kincaid grade 7.5

A salad spinner looks like a plain kitchen tool, but it is a neat lesson in motion. When you wash lettuce, drops of water cling to the leaves, but if you put the lettuce in the basket and spin it fast, the water leaves and gathers in the outer bowl. What pulls the water away? In truth, nothing does, and understanding the reason takes a close look at inertia.

Inertia is the tendency of an object to keep doing what it is already doing. A moving object keeps going in a straight line at the same speed unless some force changes its motion. A drop of water on a leaf is no different. When the basket spins, the drop wants to go straight ahead, which at any moment points along the edge of the circle rather than around it.

To make something travel in a circle, a force must keep pulling or pushing it toward the center. The basket can supply this force for the lettuce, because the leaves are held inside it, but the water is only loosely stuck to them, and the sticking is not strong enough to pull the drops around the curve, so the drops escape in straight lines and pass through the holes in the basket.

The same rule explains why a car passenger seems to slide toward the outside of a turn. The car turns, and the passenger's body tries to keep going straight until the door or seat belt pushes inward. Nothing flings the passenger outward. The body simply obeys inertia.

■ Harder · 262 words · Flesch-Kincaid grade 8

A salad spinner may look like an ordinary kitchen gadget, but it offers a neat lesson about motion. After lettuce is washed, droplets cling stubbornly to the leaves. Place the lettuce in the basket, spin it rapidly, and the water departs from the leaves and collects in the outer bowl. What drags the water away? Strictly speaking, nothing does, and understanding why requires a careful look at inertia.

Inertia is the tendency of an object to continue doing whatever it is already doing. A moving object keeps traveling in a straight line at a constant speed unless some force alters its motion. A droplet of water on a leaf is no exception. When the basket spins, the droplet tends to continue straight ahead, and at any given instant, straight ahead points along the edge of the circle instead of around it.

To make something travel in a circle, a force must continually pull or push it toward the center. The basket can supply this for the lettuce, because the leaves are held firmly in place. The water, however, is only loosely attached to them, and that weak attachment is not strong enough to haul the droplets around the curve. They escape in straight lines and pass out through the holes in the basket.

The same principle explains why a car passenger seems to slide toward the outside of a turn. The car turns, but the passenger's body tries to keep moving straight until the door or the seat belt pushes inward. Nothing flings the passenger outward. The body is simply obeying inertia.

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 inertia, force, curve, basket and obeys 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 3 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 4 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 "Why Water Stays in a Spinning Salad Spinner"?

It was written for 8th grade. It has 258 words and works out to a Flesch-Kincaid grade level of about 7.5. 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 3 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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