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Skate Science Day: The Floating Model Skateboard

Grade 8 fields practice: analyze tests of a model skateboard floating on magnets, judge the experimental design and explain forces across a gap.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS2-5

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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, Circle the answer, Sorting, Short answer

About this worksheet

What students practice

Students use investigation data to show that magnets exert forces on each other across a gap through a field.
Students evaluate an experimental design, including controls and sources of error.

How to use

Read the exhibit notes together and ask students what each extra test was meant to rule out. The design questions in Part 2 work well in small groups.

Curriculum

NGSS standard covered

MS-PS2-5

Investigate how fields let objects exert electric and magnetic forces on each other without touching.

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Skate Science Day: The Floating Model Skateboard

Investigate a magnet board that floats over a track, and judge how well the tests were designed.

Part 1: The floating board

Read the exhibit notes and study the table. Then answer the questions.

Exhibit Notes: A Board That Never Touches the Track

1Every August, the Millbrook city skate park holds Skate Science Day, when local teens set up hands-on exhibits next to the ramps. This year the park's skate club built a tabletop model of a hoverboard. The board is a 15 cm foam model skateboard with four small disc magnets glued under it, and the track is a 1 m wooden strip lined with two rows of magnets. Every track magnet has its north pole facing up, and every board magnet has its north pole facing down. Low plastic rails along the sides keep the board from sliding off. When the board is set on the track, it floats above it, and a light tap sends it gliding from one end to the other.

2Club members Dashiell Quaye and Renata Sokolova wanted evidence that the track and the board push on each other through a magnetic field, even though they never touch. The board and its magnets have a mass of 20 g. In Test 1, they stacked 5 g coins at the center of the board and measured the gap between the top of the track and the bottom of the board with a plastic ruler. For each load, they lifted the board off, set it down at the center of the track and measured again, three times in all.

3They also ran three extra tests. First, they built a control board with the same size and mass, but with plain wooden discs where the magnets would be. It rested flat on the track. Second, they built a board with its magnets turned over, so their south poles faced down. It snapped down onto the track and stuck, and it took a pull of about 1.5 N to lift it off. Third, they slid a sheet of paper across the track under the floating magnet board, and the board kept floating.

4A second group tested a copy of the exhibit, but they measured the gaps with a steel ruler, and they stacked all their coins on the front end of the board. Later, on a dry afternoon, a volunteer polished the clear plastic cover of the exhibit case with a wool cloth. Afterward, bits of foam dust jumped up to the cover from about 2 cm away.

Test 1. Gap under the magnet board
Load added (g)	Trial 1 (mm)	Trial 2 (mm)	Trial 3 (mm)	Average gap (mm)
0	12	12	12	12
10	9	10	8	9
20	7	7	7	7
40	5	4	6	?

Which result is the best evidence that the track's magnets push on the board through a field, without touching it?

A. A light tap sent the magnet board gliding from one end of the track to the other.
B. The low plastic rails kept the magnet board from sliding off the side of the track.
C. The magnet board floated 12 mm above the track, but the control board rested flat on it.
D. The coins were stacked at the center of the magnet board for every load in Test 1.