Physics: Gravity: How Mass and Distance Affect It
Explore how gravity changes with mass and distance
Physics: Gravity: How Mass and Distance Affect It
Explore how gravity changes with mass and distance
Physics - Grade 6-8
- 1
Two objects attract each other with gravity. Object A has a mass of 5 kg, and object B has a mass of 10 kg. If the mass of object A is increased to 15 kg while everything else stays the same, what happens to the gravitational force between them?
When distance and the other mass stay the same, gravitational force changes in direct proportion to the changed mass.
The gravitational force becomes 3 times stronger because object A's mass increases from 5 kg to 15 kg, which is 3 times as much. - 2
A planet and a moon are held together by gravity. If the distance between their centers doubles, what happens to the strength of the gravitational force between them?
Use the pattern that distance affects gravity by the square of the change in distance.
The gravitational force becomes one fourth as strong because gravity follows an inverse square relationship with distance. Doubling the distance makes the force 1 divided by 2 squared, or 1/4, of the original force. - 3
Explain why Earth pulls on you with more gravitational force than a small asteroid does.
Earth pulls on you with more gravitational force because Earth has much more mass than a small asteroid. More mass produces a stronger gravitational pull when distance is similar. - 4
Two identical satellites orbit Earth. Satellite X is closer to Earth, and Satellite Y is farther from Earth. Which satellite feels a stronger gravitational pull from Earth, and why?
The satellites have the same mass, so compare only their distances from Earth.
Satellite X feels a stronger gravitational pull because it is closer to Earth. Gravitational force decreases as the distance between the centers of two objects increases. - 5
A spacecraft travels away from Earth. As its distance from Earth's center increases, describe how Earth's gravitational pull on the spacecraft changes.
Earth's gravitational pull on the spacecraft gets weaker as the spacecraft moves farther away. The pull never suddenly becomes zero, but it becomes smaller with distance. - 6
Suppose two bowling balls attract each other with a tiny gravitational force. If both bowling balls are replaced with balls that each have twice as much mass, and the distance stays the same, how does the gravitational force change?
Gravity depends on the product of the two masses.
The gravitational force becomes 4 times stronger because each mass is doubled. The effect is 2 times 2, which equals 4 times the original force. - 7
Complete the comparison: If the distance between two objects becomes 3 times larger, the gravitational force becomes what fraction of its original strength?
Use 1 divided by the distance change squared.
The gravitational force becomes 1/9 of its original strength because 3 squared is 9, so the force is divided by 9. - 8
A student says, "Only very large objects have gravity." Explain why this statement is incorrect.
The statement is incorrect because all objects with mass have gravity. Very large objects have stronger gravity, but even small objects such as pencils and books attract other objects with a tiny gravitational force. - 9
Look at the situation: Object A has a mass of 20 kg, object B has a mass of 20 kg, and they are 2 meters apart. Object C has a mass of 20 kg, object D has a mass of 20 kg, and they are 4 meters apart. Which pair has the stronger gravitational force?
Objects A and B have the stronger gravitational force because they are closer together. The masses are the same in both pairs, so the smaller distance gives the stronger force. - 10
On the Moon, your weight is less than on Earth, but your mass is the same. Explain the difference between mass and weight in this example.
Mass is measured in kilograms, while weight is a force measured in newtons.
Mass is the amount of matter in your body, so it stays the same on Earth and on the Moon. Weight is the gravitational force pulling on that mass, so it is smaller on the Moon because the Moon has less mass than Earth. - 11
Two planets have the same size, but Planet A has twice the mass of Planet B. If you stood the same distance from each planet's center, which planet would pull on you more strongly?
Planet A would pull on you more strongly because it has twice the mass of Planet B. If distance is the same, twice the mass means twice the gravitational force. - 12
Use this rule: gravitational force is proportional to mass 1 times mass 2 divided by distance squared. If the distance stays the same, and one mass is tripled while the other mass is doubled, how many times stronger is the force?
Multiply the two mass change factors.
The force becomes 6 times stronger because the mass changes multiply together. Tripling one mass and doubling the other gives 3 times 2, or 6 times the original force. - 13
A comet passes near the Sun. As the comet gets closer to the Sun, what happens to the gravitational force between the Sun and the comet?
The gravitational force increases as the comet gets closer to the Sun. A smaller distance means a stronger gravitational pull. - 14
If two objects are moved from 6 meters apart to 2 meters apart, the distance becomes one third as large. How does the gravitational force change?
Moving objects closer increases gravity by the square of the distance factor.
The gravitational force becomes 9 times stronger because the distance is reduced by a factor of 3. Since gravity depends on distance squared, 3 squared equals 9. - 15
Write a short explanation using the words mass, distance, and gravity: Why do astronauts still orbit Earth even though they are far above the surface?
Astronauts still orbit Earth because Earth has a very large mass, so its gravity reaches far into space. The force is weaker at a greater distance, but it is still strong enough to pull the astronauts and their spacecraft into orbit.