+
Mass vs. Weight and
Gravity
+
Bell work
 1.Which
is generated when a bar magnet is moved
through a wire coil?
 A. electric
current
 B. gravitational
 C. thermal
 D. solar
field
energy
energy
+
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
+ Student Learning Objectives
SPI 0807.12.5
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
+
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.
+
 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.
+ 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.
+ 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.
+ 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.
+ 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.
+ 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.
+
 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.
+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)
+
SPI 0807.12.5
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
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SPI 0807.12.5
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.
+
SPI 0807.12.5
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.
+
SPI 0807.12.5
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.
+
SPI 0807.12.5
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.
+
SPI 0807.12.5
Gravity-Mass and Distance
Here is an example of a question you might see on a quiz or test.
+
Exit Ticket
 True
 The
or false
greater the mass, the greater the
gravitational force.