Worksheet

Lead Spheres and the Pull of Gravity

Grade 8 gravity practice: analyze gravity simulator data for pairs of lead spheres and argue that gravity attracts and depends on both masses.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS2-4

Play online Play as a game

PrintLetter-size worksheet Answer keyPrintable answers

Assign to classAssign to your classes, or get a join code

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, Sorting, Short answer

About this worksheet

What students practice

Students analyze data to describe how the gravitational force between two objects depends on both masses.
Students use evidence to argue that gravity is an attractive force.

How to use

Read the passage together and point out which variable changes in each trial before students begin. Use the last question for a short class debate about the classmate's claim.

Curriculum

NGSS standard covered

MS-PS2-4

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

Preview

OwlSheets.com

Name Date

Lead Spheres and the Pull of Gravity

Use simulator data to argue that gravity attracts and depends on both masses.

The simulator data

Read the passage and study the table. Then answer the questions.

Science Night at Eastbrook Makerspace

1Every month the Eastbrook Makerspace holds a science night where members build and test simple devices. This month the theme was gravity. Volunteer engineer Elias Varga brought a wooden model of a famous device called a torsion balance. In 1798 the scientist Henry Cavendish hung a rod with a small lead ball on each end from a thin wire. He then placed two large lead balls, each about 160 kg, near the small ones. Over several minutes the small balls swung slowly toward the large balls and twisted the wire a tiny amount. By measuring the twist, Cavendish worked out the size of the force between the balls.

2The makerspace model is only for display. The real effect is so small that air currents, a slammed door or footsteps on the floor can hide it. So eighth grader Noor Castellanos ran a gravity simulator on a laptop instead. She placed two solid lead spheres, A and B, so that their centers were always 1.00 m apart. In each trial she changed the mass of one or both spheres and recorded the gravitational force between them in micronewtons (µN). One micronewton is one millionth of a newton. For comparison, a single sheet of printer paper weighs about 50,000 µN.

3In every trial the simulator drew two force arrows: one on sphere A pointing toward sphere B, and one on sphere B pointing toward sphere A. The two arrows were always the same length. Noor did not get to finish trial 6 before the laptop battery died, so that row is still blank.

4Elias added two facts from space science. Earth's mass is about 81 times the mass of the Moon, and Jupiter's mass is about 318 times the mass of Earth. When a space probe flies past a large planet, the planet pulls it inward, and the probe's path bends toward the planet before it moves away again.

Gravity Simulator Results (centers 1.00 m apart)
Trial	Mass of A (kg)	Mass of B (kg)	Force (µN)
1	1,000	1,000	67
2	2,000	1,000	133
3	3,000	1,000	200
4	4,000	1,000	267
5	2,000	2,000	267
6	4,000	2,000	?

Compare trial 1 and trial 4.

The force in trial 4 is about times the force in trial 1.

Which two trials show what happens when only the mass of sphere A changes?

A. Trials 4 and 5
B. Trials 3 and 5
C. Trials 1 and 3
D. Trials 2 and 5

Trials 4 and 5 have the same force. What does this show?

A. Both masses count: less mass in A and more in B gave the same pull.
B. The larger of the two spheres sets the size of the force by itself.
C. The force depends on which of the two spheres is labeled A.
D. The force stops growing once one sphere reaches 4,000 kg of mass.

Sort each statement. Use only the simulator results in the passage and the table.

With sphere B kept at 1,000 kg, the force grows as the mass of A grows.In some trials the two spheres pushed each other apart.With sphere A kept at 2,000 kg, doubling the mass of B doubles the force.Moving the spheres farther apart makes the force weaker.Sphere B pulls on sphere A as hard as sphere A pulls on sphere B.

Shown by the simulator	Not shown by the simulator

Two students with masses of about 50 kg each sit 1 m apart. Neither one feels pulled toward the other. Which explanation fits the data best?

A. The air between the two students blocks most of the pull of gravity.
B. Students have far less mass than the spheres, so the pull is tiny.
C. An object needs a mass of 1,000 kg before it pulls on anything.
D. Gravity acts between planets and moons but not between people.

Use the patterns in the table to predict the force in trial 6.

A. About 1,070 µN
B. About 530 µN
C. About 400 µN
D. About 270 µN

Gravity beyond the lab

Use the passage, the table and the patterns you found to answer.

Which observation from the passage is the best evidence that gravity pulls objects toward each other?

A. A probe flying past Jupiter is pushed onto a path that bends away from it.
B. A magnet across a table pulls a steel paper clip toward it.
C. The large lead balls pushed the small balls away and twisted the wire.
D. In Cavendish's device the small balls slowly swung toward the large balls.

Suppose the Moon had twice its real mass but stayed the same distance from Earth.

The gravitational force between Earth and the Moon would be times as strong as it is now.

A space probe passes 1 million km from the center of Jupiter. Months later it passes 1 million km from the center of Earth. How do the two pulls on the probe compare?

A. The pull from Jupiter is about 318 times as strong as Earth's pull.
B. The pull from Earth is stronger, because Earth is rocky and solid.
C. The pull from Jupiter is about 318 times weaker than Earth's pull.
D. The pulls are equal, because the probe's own mass did not change.

10.

A makerspace member claims: "The pull of gravity depends on the bigger object. The mass of the smaller object does not matter." Do you agree? Write a claim, give evidence from at least two trials in the table, and explain your reasoning.