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Jump Lab: Sending Force Plate Data Across Campus

Grade 8 practice: a sports science lab compares analog and digital force plate readings and sampling settings to explain why digital signals are more reliable.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS4-3

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What’s included

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

Details

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

About this worksheet

What students practice

Students use test data to explain why noise changes analog readings but not digital ones.
Students explain how sampling affects a digitized signal and argue from evidence which system is more reliable.

How to use

Read the lab notes together and check that students can turn a force into a voltage. Then let them work through both tests and finish with the claim-evidence-reasoning task.

Curriculum

NGSS standard covered

MS-PS4-3

Explain why digital signals carry information more reliably than analog signals.

Preview

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Jump Lab: Sending Force Plate Data Across Campus

Use sports lab data to explain why digitized signals carry information more reliably than analog ones.

Part 1: Two ways down the same cable

Read the lab notes. Use paragraphs 1–3 and Table 1 for questions 1–6.

From the Force Plate to the Coach's Screen

1Every summer, eighth grader Inez Thornbury spends two weeks at a sports science camp in a university lab run by Dr. Wendell Ambrose. Campers measure balls, bats and runners: a radar gun clocks pitches, timing gates time sprints, and a force plate measures jumps. A force plate is a flat metal platform with sensors under it. It measures how hard an athlete pushes on the ground, in newtons (N). Coaches use the biggest push in a jump, called the peak force, to track how an athlete's legs are getting stronger.

2The sensors in the force plate make an analog signal: a voltage that rises and falls smoothly as the force changes, at 1 V for every 500 N. The lab's old system sends this voltage along a 150 m cable to the coaching room in another building, where a screen turns each voltage back into a force. Any unwanted change added to the voltage along the way, called noise, changes the force on the screen. The lab's new system first digitizes the signal at the plate. Many times each second it measures the voltage and turns it into a number, then sends each number as a pattern of electric pulses that stand for 0s and 1s. The receiver only has to decide whether each pulse is there or not, then rebuilds the numbers.

3To compare the two systems, Dr. Ambrose asked five campers to do one jump each. A meter wired straight to the plate showed each true peak force. Both systems sent the same jumps to the coaching room at the same time, through cables that run side by side past the building's elevator motors, which cause electrical noise. The new system took 1,000 samples each second. Table 1 shows the results.

4The new system has a setting for how many samples it takes each second. For Test 2, Inez recorded one of her own jumps at three settings at once, and the screen drew the force curve by joining the samples with lines. The meter at the plate showed a true peak force of 1,300 N. The peak of a jump lasts only a small fraction of a second. Table 2 shows the peak force on the screen for each setting.