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Why the Front of a Car Is Built to Crumple

5th grade nonfiction passage about forces and stopping time: 223 words, six questions, an answer key and vocabulary.

5th grade nonfiction forces and stopping time 223 words

Why the Front of a Car Is Built to Crumple

Cars are built to be strong, yet the front and back of many are designed to crumple like a squeezed paper cup when something hits them hard. That seems backward. Wouldn't a stiffer car be safer? Engineers found that the answer is no, and the reason comes from the science of forces.

A moving car, and everyone riding in it, has motion energy. In a sudden stop, that motion must be removed. How quickly it is removed changes how big the push on the passengers is. Stopping in a very short time takes a huge force. Stopping over a longer time takes a smaller force.

Think about dropping an egg. On a hard floor, it stops almost instantly and cracks. Onto a thick pillow, it takes longer to slow down, and it is far less likely to break. The pillow does not remove any less motion. It spreads the stopping out over more time.

A crumple zone works like the pillow. As the front of the car folds, it uses up the motion energy slowly, so the passengers slow down more gently. Meanwhile, the middle of the car, where people sit, is made extra strong so that it keeps its shape. Seat belts hold people in place so that they slow down along with the car. Together, these parts help keep riders safe.

Questions

  1. What is a crumple zone? in the text

  2. Which takes a huge force, stopping in a very short time or over a longer time? in the text

  3. Why does an egg crack on a hard floor? in the text

  4. How is a crumple zone like a thick pillow? think about it

  5. Why is the middle of the car made extra strong? in the text

  6. What do seat belts do in a sudden stop? in the text

Words to know

crumple
to fold up and wrinkle when pressed
engineer
a person who designs and builds things
force
a push or a pull on something
passenger
a person riding in a vehicle
stiff
hard to bend or fold
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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 · 210 words · Flesch-Kincaid grade 3

Cars are built to be strong. Yet the front and back of many cars are made to crumple when something hits them hard. They fold like a squeezed paper cup. That seems backward. Wouldn't a stiff car be safer? Engineers found it would not. The reason comes from forces.

A moving car and the people in it have motion energy. In a sudden stop, that motion must be taken away. How fast it is taken away changes the size of the push on the passengers. A very short stop takes a huge force. A longer stop takes a smaller force.

Think about dropping an egg. On a hard floor, it stops at once and cracks. Onto a thick pillow, it takes longer to slow down. It is much less likely to break. The pillow does not take away less motion. It spreads the stopping over more time.

A crumple zone works like the pillow. The front of the car folds and uses up the motion energy slowly. The passengers slow down more gently. The middle of the car, where people sit, is made extra strong so it keeps its shape. Seat belts hold people in place so they slow down with the car. Together, these parts help keep riders safe.

▲ This passage · 223 words · Flesch-Kincaid grade 4.6

Cars are built to be strong, yet the front and back of many are designed to crumple like a squeezed paper cup when something hits them hard. That seems backward. Wouldn't a stiffer car be safer? Engineers found that the answer is no, and the reason comes from the science of forces.

A moving car, and everyone riding in it, has motion energy. In a sudden stop, that motion must be removed. How quickly it is removed changes how big the push on the passengers is. Stopping in a very short time takes a huge force. Stopping over a longer time takes a smaller force.

Think about dropping an egg. On a hard floor, it stops almost instantly and cracks. Onto a thick pillow, it takes longer to slow down, and it is far less likely to break. The pillow does not remove any less motion. It spreads the stopping out over more time.

A crumple zone works like the pillow. As the front of the car folds, it uses up the motion energy slowly, so the passengers slow down more gently. Meanwhile, the middle of the car, where people sit, is made extra strong so that it keeps its shape. Seat belts hold people in place so that they slow down along with the car. Together, these parts help keep riders safe.

■ Harder · 249 words · Flesch-Kincaid grade 8.6

Automobiles are built to be sturdy, and yet the front and rear sections of many are deliberately designed to crumple like a squeezed paper cup whenever something strikes them forcefully. This seems counterintuitive, since a stiffer car might appear safer. Engineers discovered, however, that the opposite is true, and the explanation comes from the science of forces.

A moving car, along with everyone riding inside it, carries motion energy. During a sudden stop, all of that motion has to be removed, and the speed at which it is removed determines how large a push the passengers feel. Stopping in an extremely short span of time requires an enormous force, whereas stopping over a longer span requires a much smaller one.

Consider what happens when an egg is dropped. On a hard floor it halts almost instantly and cracks. Onto a thick pillow, it takes longer to slow down and is far less likely to break. The pillow does not absorb any less motion; it simply stretches the stopping out over a greater amount of time.

A crumple zone operates in the same way as the pillow. As the front of the car folds, it gradually consumes the motion energy, so the passengers decelerate more gently. Meanwhile, the central part of the car, where people sit, is reinforced so that it holds its shape. Seat belts keep people in place so that they slow down together with the vehicle. All of these parts work as a team to protect riders.

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 crumple, engineer, force, passenger and stiff 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 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 the Front of a Car Is Built to Crumple"?

It was written for 5th grade. It has 223 words and works out to a Flesch-Kincaid grade level of about 4.6. 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. 5 ask for something the text says directly and 1 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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