Earth Space Science: 08 Our Solar System: 08.02 Forces in Our Solar System

Forces in Our Solar System Lab Report


Gravity is the force of attraction that pulls objects toward the center of Earth and that holds the moon in orbit around Earth. Galileo was interested in understanding gravity. He assumed all objects are subject to the same acceleration due to gravity. The objective of this lab assignment is to determine if objects with different masses fall at the same rate or varying rates in the presence of air and in a vacuum.


What effect does Earth’s gravitational force have on objects of different masses?


For your hypothesis, predict what will happen to the acceleration of objects in normal mode and vacuum mode.

For example:

If I drop two objects in normal mode, their acceleration to the ground will ____________________.

If I drop two objects in vacuum mode, their acceleration to the ground will ___________________.


Gravity virtual lab activity

Familiarize yourself with the virtual lab activity.
Using the virtual activity, choose two different objects from the upper left-hand corner (the feather, big ball, and small ball).
Drag your objects into Galileo’s hands and select “DROP.” Record your observations on Table 1.
Repeat three times with different combinations.
Select the “VACUUM MODE” and repeat steps 2 through 4 with the same objects you used in trials one through three.
Record your observations in Table 1.
Complete the Questions and Conclusion section of the lab report.

For this investigation, list the independent, dependent, and controlled variables.

Data and Observations:

Table 1: Gravity Test Trials

Questions and Conclusion

What force/s were acting on the objects dropped in the air (normal mode)? What force/s was acting on the objects dropped in the vacuum?
Why was there a difference between the normal mode and the vacuum mode?
Explain how objects on Earth accelerate compared to objects in the vacuum of space. Be sure to use Newton’s laws of motion to support your explanations.
The gravitational pull of Jupiter is greater than the gravitational pull of Earth. How would adding a “JUPITER MODE” to the virtual activity change the results of Galileo’s experiment?
How did your hypotheses match your observations of falling objects in air and in a vacuum?
Describe other ways you could investigate the acceleration of objects due to gravity.
Forces in Our Solar System

Ben and Kelly were watching news of a satellite being launched into space. Wondering about the launch, they started talking about gravity. This is what they said:

08.02 Forces in Our Solar System
Text Version for Conversation between Ben and Kelly
Ben: Gravity needs an atmosphere or air. If there is no atmosphere, there is no gravity.
Kelly: Gravity does not require an atmosphere or air. If there is no air, there will still be gravity.

Show Video
Now that you’ve heard two different views, think about which one makes more sense to you.

Let’s see which friend is correct.

Physical forces govern all of the parts of the solar system. The solar system is affected by these physical forces in a variety of ways. In this lesson, you will investigate the effects of physical forces on objects within the solar system.


How do forces impact our solar system?
At the end of this lesson, you will be able to:
define the role of gravitational forces in our solar system
identify electromagnetic forces and their effects in our solar system
Photograph of astronauts floating in space
Public Domain

Gravity is a universal physical force that is responsible for the following phenomena:

Gravity holds you to the surface of Earth.
Gravity keeps planets in orbit.
Gravity causes nebulae to collapse, forming new stars.
In the image above, the astronauts do not appear to be experiencing gravity, but they are! All objects with mass are affected by gravity. As the astronauts move away from Earth, they experience a decrease in the planet’s gravitational force. But gravity is still present.

In space astronauts experience microgravity. The distance from Earth decreases the pull of gravity, so it is much less than on the planet’s surface.

There is one more factor that comes into play. On Earth, we have a force called air resistance that can slow down the speed of falling objects.

Air resistance is caused by the friction between a falling object and the particles in air. The amount of air resistance a falling object experiences is based on the shape of the object and the speed at which it falls.

All objects, regardless of their mass, experience the same acceleration when in a state of free fall. When the only force is gravity, and there is no air resistance, the acceleration is the same value for all objects. In order to remove air resistance, we would need to drop the objects without the presence of air.

Scientists can use a container called a vacuum, a chamber from which nearly all air has been removed, to remove the friction caused by air resistance. You can test this for yourself in the virtual gravity lab.

Several key figures in scientific history have contributed to the understanding of gravity as we know it today, including Galileo Galilei, Sir Isaac Newton, and Albert Einstein.

Galileo Galilei (1564–1642) was a scientist, philosopher, and mathematician. His observations of the movement of objects on Earth led him to conclude that all objects accelerate as they fall. Acceleration is an increase in speed over time. Today we know that acceleration is due to gravity. The rate of acceleration due to gravity is the same wherever you are on Earth. Galileo concluded that all objects, regardless of their weight, would fall to Earth at the same rate of acceleration.

Had Galileo lived today, he would see that our understanding of gravity has increased. Astronauts, while on the moon, conducted an experiment and finally proved Galileo to be correct for locations beyond Earth. View the following video to see how they did it.

Sir Isaac Newton (1642–1727) was the first scientist to provide an explanation for observations of the movement of planets within the solar system. As had other scientists before him, Newton observed that planets moved in an orbital path around the sun. However, he was not satisfied with only a description of how the planets moved.

Newton wanted to know why the planets moved as they did. He theorized that something must be holding the planets in their orbits. The force he called gravity was what caused the planets to remain in orbit.

For Newton, gravity’s effect on the movement of the planets is an example of his First Law of Motion.

First Law of Motion

The inertia Newton observed in the planets is defined as an object’s resistance to a change in speed or direction unless the object is acted upon by another force. This force is gravity. The sun keeps the planets locked within their orbits, moving at relatively the same speed and direction year after year.

Newton also devised other laws of motion. In his Second Law, Newton figured out the relationship between the mass of an object and its acceleration.

Second Law of Motion

This equation shows that gravity, mass, and acceleration are related. The greater the mass of an object, the greater the force necessary to move it. For example, suppose you wanted to push a pencil across a desk with your finger. This would not require too much force. If you applied the same force to a brick, however, the brick would not move. In space, gravity is the universal force that causes objects to accelerate. In space travel, rockets must be able to lift off the ground.

This requires some hefty lift capacities to create enough force to move them upward and away from Earth.

Gravity is a function of space, time, energy, and mass. According to the model developed by Albert Einstein (1879–1955), time and space are intricately related. Called the space-time continuum, time and space can be thought of as a sort of fabric. Objects within time and space will bend this “fabric,” creating a gravitational force.

Use the activity below to investigate how gravity works in space:

08.02 Forces in Our Solar System
Text Version for Modeling the Space-Time Continuum Interactive
An interactive in which objects with different masses are placed on a stretched piece of fabric representing the space-time continuum.

A small marble causes the fabric to curve slightly downward; a medium-sized tennis ball causes the fabric to curve even more downward; a large bowling ball causes the fabric to curve mostly downward.

Show Interactive

The greater the mass, the larger the pull of gravity. This leads to one of the fundamental laws of nature:

Mass and gravity are related. The greater the masses, the greater the gravitational force.

One way to envision the effects of gravity on mass is to imagine taking a trip to another planet. The mass of a planet affects the planet’s gravitational force, and therefore the weight of an object on the planet. Weight is defined as the pull of gravity on a mass. On Earth, gravity does not change significantly, so your weight stays relatively the same from one minute to the next. On other planets or moons, the gravitational pull can be greater than or less than that of Earth, so your weight changes on other planets even though your mass stays the same.

Use the following activity to investigate weight changes throughout the solar system:

Flip the card to see how weight changes throughout the Solar System.
Weight Changes Throughout the Solar System

Ever wonder what it would be like to live on another planet? I bet it would be really different. I know one thing that would be really different—your weight! Select the image to flip and find out!

Astronaut, Earth, Moon, Mars, Jupiter, Saturn

The astronaut’s weight changes depending on his location in the solar system:

Earth: 100 lbs
Jupiter: 250 lbs
Moon: 16 lbs
Saturn: 110 lbs
Mars: 40 lbs
Show Text Version
As you saw earlier in the lesson, distances between objects also affect gravitational force. For example, the further an astronaut travels from Earth, the smaller the gravitational force acting upon the astronaut. The closer two objects are, the greater the gravitational force. The contraction of the nebula that formed the solar system happened according to the same principle. As gas and dust moved closer together, their gravitational attraction increased. Eventually, the strength of this attraction formed the sun.

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The objective of this lab assignment is to determine if objects with different masses fall at the same rate or varying rates in the presence of air and in a vacuum.


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The objective of this lab assignment is to determine if objects with different masses fall at the same rate or varying rates in the presence of air and in a vacuum. was last modified: by