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Helmet Design Lab: Magnet Buckles, Magnet Cushions and Stored Energy

Grade 8 potential energy practice: graphs of a magnetic chin buckle and a repelling-magnet cushion, plus a drop rig, model how distance changes stored energy.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS3-2

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
11 questions
Classroom-ready

Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students read graphs to model how the gap between attracting or repelling magnets changes stored energy.
Students compare magnetic and gravitational systems to explain when moving objects apart stores more energy.
Students use stored-energy data to argue which cushion design takes up more energy from a bump.

How to use

Before students start, model each graph with two real magnets: let them feel the pull grow as attracting magnets come together and the push grow as repelling magnets are squeezed.

Curriculum

NGSS standard covered

MS-PS3-2

Model how changing the distance between interacting objects changes the potential energy stored in the system.

Preview

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Name Date

Helmet Design Lab: Magnet Buckles, Magnet Cushions and Stored Energy

Read two graphs and a drop-rig table to model how distance changes the energy stored in a system.

Graph 1: The magnetic chin buckle

Read the club's design notes and study Graph 1. Then answer the questions.

Design Notes: A Helmet People Will Actually Wear

1The bike-safety club at Larkspur Middle School surveyed riders at the school bike rack. Many said they skip the chin strap because the plastic clip is hard to close with gloves on. Club president Emeric Vasquez proposed a helmet with two magnet parts: a chin buckle that snaps shut by itself, and a cushion of magnets between the hard outer shell and the foam liner. The club advisor, Ms. Ingrid Achebe, asked the members to model the potential energy in each design. Potential energy is energy stored in a system of objects that push or pull on each other, and the amount depends on how the objects are arranged. She also reminded them that the foam liner would still do most of the work of protecting a head in a crash; the magnet cushion is meant only to soften small everyday bumps.

2The buckle has two halves, each with a small magnet inside, set so that the halves attract. The club held one half still and used a force sensor to pull the other half away in small steps. Ms. Achebe's spreadsheet turned the force readings into the energy stored in the system of the two halves, compared with the halves touching. Graph 1 shows the result. When a rider lets go of the free half anywhere within about 10 mm, it snaps onto the other half with a click.

3For the cushion, the club glued pairs of magnets to the inside of the shell and the outside of the liner, set so that each pair repels. Pushing the shell toward the liner squeezes the magnets closer together. The club measured the push needed at each gap, and the spreadsheet turned it into the energy stored in one pair, compared with the magnets far apart. Graph 2 shows the result. When the club released a squeezed pair, the magnets sprang apart again.

4The club also borrowed a drop rig from a nearby college lab. A winch lifts a 5.0 kg test headform wearing a helmet above a steel block, then lets it fall. The rig's display shows the energy stored in the system of the headform and Earth, compared with the headform resting on the block. The club recorded the display at four heights, rounded to the nearest joule.