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The Tug From a Passing Truck: Is It Gravity?

Grade 8 gravity practice: a bike-safety club tests the claim that a passing truck's gravity tugs riders, using ride notes and gravity calculator data.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS2-4

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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, Sorting, Short answer

About this worksheet

What students practice

Students use data to show that the gravitational pull between two objects grows with the mass of each object.
Students argue from evidence that gravity attracts and that everyday objects pull on each other only very weakly.

How to use

Have students list what they would expect if the tug really were gravity before they read the ride notes, then check those predictions against the evidence.

Curriculum

NGSS standard covered

MS-PS2-4

Argue from evidence that gravity is attractive and depends on the masses of the objects.

Preview

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Name Date

The Tug From a Passing Truck: Is It Gravity?

Argue from evidence about what gravity does and what its strength depends on.

The ride notes and the gravity calculator

Read the club's notes and Table 1, then answer the questions.

Bike-Safety Club Notes: What Tugged on Us?

1The bike-safety club at Fairmount Middle School is designing a better helmet and a set of safe-riding tips for younger riders. Last Saturday, adviser Ms. Harriet Obi led the club on a group ride along the wide paved shoulder of a county road. Several times, a large box truck rushed past. Riders felt a sudden shove away from the road as each truck arrived and then a tug toward the road after it went by. A small car passing at the same speed gave only a light tug, and slower trucks gave weaker tugs than fast ones.

2Eighth grader Darius Kemal had an explanation. "That was the truck's gravity pulling on us," he said. "Gravity depends on mass, and a truck has a huge mass." His teammate Lucinda Farah was not so sure. She reminded the club that a good argument needs a claim backed by evidence, not just a feeling, and the helmet team agreed to put off testing visor shapes until the question was settled. At a rest stop, the club stood about 2 m from a parked truck of the same size for ten minutes, and nobody felt any tug at all.

3Back at school, the club used an online gravity calculator. It treats each object as if all of its mass sat at one point and finds the pull of gravity between two objects whose centers are 2 m apart. The pulls are tiny, so the calculator gives them in micronewtons (µN); one micronewton is one millionth of a newton. Each object in a pair pulls on the other with the same force. To check the calculator, the club entered the masses of Earth and the Moon and the distance between them, and it gave a pull close to the value in their textbook.

4For comparison, the club weighed its riders with their bikes on a platform scale. Earth pulls on Lucinda and her bike, 40 kg in all, with about 390 N, and on Darius and his bike, 80 kg in all, with about 780 N. Earth has a mass of about 6 × 10²⁴ kg.

5Ms. Obi added two more observations from the ride. A water bottle that slipped out of a cage fell straight down to the road, and riders who stopped pedaling on a downhill stretch kept speeding up.

Table 1. Gravity calculator, centers 2 m apart
Pair	Object 1 (kg)	Object 2 (kg)	Pull on each (µN)
A: rider and rider	80	80	0.11
B: rider and car	80	1500	2
C: rider and truck	80	15000	20
D: rider and truck	40	15000	10

Use paragraphs 1 and 2. Circle the three observations that go against Darius's idea that the tug came from the truck's gravity.

Nobody felt a tug standing 2 m from a parked truck of the same size.The truck had far more mass than the small car.Riders were shoved away from the road as each truck arrived.The riders stayed on the wide paved shoulder of the road.Slower trucks gave weaker tugs than fast trucks of the same kind.

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