1. Mass vs. Weight and Gravity

2. Bell work
1. Which is generated when a bar magnet is moved through a wire coil?
A. electric current
B. gravitational field
C. thermal energy
D. solar energy

3. Bell work
1. Which is generated when a bar magnet is moved through a wire coil?
A. electric current
B. gravitational field
C. thermal energy
D. solar energy

4. Student Learning Objectives
SPI
Gravity-Mass and Distance
Tennessee SPI Objective:
Determine the relationship among the mass of objects, the distance between these objects, and the amount of
gravitational attraction.
Check for Understanding
Identify factors that influence the amount of
gravitational force between objects
Essential Question(s)
What is gravity? What is mass? How does mass and
distance affect gravitational pull?
TOC: Mass vs. weight and Gravity notes

5. Mass vs. Weight? (video) Mass is how much matter is in an object.
Weight is the measurement of the gravitational force.
Mass is a physical property of all matter that exists in the universe. It is commonly measured in kilograms. Regardless of where an object is located, the mass of the object at any given time remains the same
. For example, if a person had a mass of 45 kg on the surface of the Earth, that person’s mass would also be 45 kg on the moon, or even in outer space.

6. Unlike mass, the weight of an object can change based on where the object is located. Weight is the amount of gravitational pull on an object. It is commonly measured in newtons or pounds. So depending on where an object is, the gravitational force acting on it could be different and, accordingly, its weight could be different.
Since the gravitational force acting on an object is proportional to its mass, the weight of an object is proportional to its mass as well.

7. Gravity in the Solar System
The universal law of gravitation states that every object with mass exerts a gravitational force on every other object with mass in the universe.
Gravity plays a vital role in the formation and movement of the planets, stars, and solar systems. Stars, planets, galaxies, and galaxy clusters are all formed and held together by gravity.
Gravity is a force among all objects in the universe. Within our solar system, every object is attracted to every other object due to gravity. The closer objects are and the more mass they have, the stronger the attraction. Variations in gravitational forces among objects in the solar system cause variations in the objects’ orbital speeds.

8. Mass vs. Gravity
The greater the total mass of two objects is, the greater the gravitational force between them. For example, a meteoroid positioned halfway between two asteroids will be attracted more to the asteroid with greater mass.
The difference in mass between two objects can also affect how gravity affects the objects’ motion. The motion of the less massive object is more affected by the force than is the motion of the more massive object. For example, the planet Jupiter is much more massive than its moons. This is why each of its moons orbit around the planet. The gravitational force between Jupiter and its moons does affect the motion of Jupiter, but only slightly.
Another example of this is the orbits of all the planets around the Sun. The Sun is the most massive object in the solar system. This causes all the planet-moon systems, asteroids, meteoroids, and comets to orbit around the Sun. The Sun moves only slightly due to the gravitational force between it and the planets. Because of this, the Sun stays in the central part of the solar system while the planets move in large orbits around it.

9. Distance & Gravity
The shorter the distance between two objects, the stronger the gravitational force between them. For example, because the Moon’s orbit is elliptical, the gravitational force between the Earth and the Moon is stronger when the Moon is closer to the Earth. When the Moon is farther away in its orbit, the gravitational force between it and the Earth is weaker.

10. Distance & Mass
Both distance and mass influence the gravitational force between two objects at the same time. Differences in distance have a greater effect on gravity than do the differences in mass. For example, the gravitational force between the Earth and Moon is stronger than the force between the Earth and the Sun. Even though the Sun has such a great mass, the shorter distance between the Earth and the Moon makes the force between the Earth and Moon much stronger than the force between the Earth and the Sun.

11. Gravity & Motion
The Sun contains most of the mass in the solar system. Accordingly, the Sun exerts a very strong gravitational force on the other objects in the solar system. Over time, many objects, including the planets, have settled into stable orbits around the Sun.
Each moon in the Solar System orbits a planet and also orbits the Sun. As a moon orbits its planet, the planet moves around the Sun. So a moon orbits the Sun at the same time as it orbits its planet.
The sun is the only object in the Solar System that is essentially stationary relative to the Solar System as a whole. As the Sun slowly orbits the center of the galaxy, the entire Solar System comes along with it. So, relative to the planets, moons, asteroids, and comets of the Solar System, the Sun does not move.

12. The gravitational force between a planet and the Sun, along with the planet’s inertia (continued forward motion), keeps the planet moving in orbit around the Sun. Without the Sun’s gravity, a planet’s inertia would send it traveling in a straight line off into space. Without a planet’s inertia, the Sun’s gravity would pull the planet straight toward it, and the two would collide.
Each planet’s orbit is shaped like an ellipse, which is nearly circular. This gravitational force also determines the planet’s orbital speed. The gravity between planets and the Sun is stronger for planets closer to the Sun than for planets farther away from the Sun. The stronger the force the faster the orbital speed.

13. Gravity and the Theory of Relativity
F.Y.I. -Einstein theorized that mass warps (bends/curves) space and this warping explains the force we call gravity.
1)Link: Curvature of Space-Time (34 sec)
2)Link: How Gravity Really Works (1 min 45 sec)

14. Gravity-Mass and Distance
SPI
Gravity-Mass and Distance
1) What is the name of the law about gravity? The law of…
A) …Conservation of Mass or B) …Universal Gravitation
(2) All matter in the universe attracts other matter by?
A) A “pushing force” or B) A “pulling force”
(3) The strength of gravity depends on the ______ of the objects
A) Masses or B) Shape
4) Effect of gravity depends on the _____ between the objects.
A) Energy or B) Distance
5) What did Einstein say about mass and gravity?
A) That mass warps space or B) Mass and gravity are the same

15. Gravity-Mass and Distance
SPI
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.

16. Gravity-Mass and Distance
SPI
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.

17. Gravity-Mass and Distance
SPI
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.

18. Gravity-Mass and Distance
SPI
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.

19. Gravity-Mass and Distance
SPI
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.

20. Exit Ticket True or false
The greater the mass, the greater the gravitational force.