ASTRO 7N
Astro 7N Revised Exam 1 2025
The force of gravity by the Sun keeps the planet in orbit around it, but how do the
planets affect the sun? - -They exert an equally strong pull on the sun, causing it move
slightly
Newton's First Law - -An object at rest stays at rest and an object in motion stays in
motion with the same speed and in the same direction unless acted upon by an
unbalanced force.
ex: if the sun suddenly disappeared, the Earth would continue in the direction that it was
traveling in its orbit at that time
Newton's Second Law - -The acceleration of a body due to a force will be in the same
direction as the force, with magnitude directly proportional to its mass
Force = mass x acceleration
A smaller mas will move faster, if the same force is applied to it
Newton's Third Law - -For every action there is an equal and opposite reaction
The Sun exerts force on planets, and they orbit it - he planets exert equal force on Sun,
but it only moves slightly because of its very large mass relative to the planets
Surface Gravity on a Planet - -the strength of gravity: g = m/r^2
Where M is the mass of the planet and R is its radius. Note the radius is squared but the
mass is not.
More mass = more gravity.
- If the mass of a planet were twice that of another, but they had the same radius, the
gravity felt on the surface of the more-massive one would be twice as strong.
Larger separation = less gravity.
- If the radius of a planet were twice that of another, the gravity is 1 / (2) 2 = 1/4 as
strong.
Putting the effects of mass and radius together, you should be able to figure out the
surface gravity of Mars, relative to the Earth.
- Mars has 1/10 the mass of the Earth and 1/2 the radius of Earth. So for Mars,
g = (1/10) / (1/2) 2 = (1/10) / (1/4) = 4/10
ASTRO 7N
,ASTRO 7N
Mars has a surface gravity 4/10 that of Earth. You will need to be able to do this type of
estimate for the test, given the numbers for mass and radius.
If I apply exactly the same amount of force to a pebble and a boulder, what will happen -
-the pebble will move faster
If the Earth were moved to half its current distance from the sun, how would the force of
gravity by the sun on the earth change? - -it would become 4 times weaker
Mass - -As the mass of the planet increases, the jump height does decreases by the
same factor
As the mass of the planet decreases, the jump height does increases by the same
factor
According to Newton's Second law of motion, if the net force acting on the object
increases while the mass of the object remains constant, what happens to acceleration -
-acceleration increases
If the earth were moves to half its current distance from the Sun, how would the force of
gravity by the Sun on the Earth change - -it would become four times weaker
What did newton's law of universal gravitation tell us about how gravity works - -the
force of gravity from the sun will be stronger on object with more mass
If you were to sit on the ground, there would be a force due to gravity pulling you toward
the earth. which of the following is true according to newton's third law - -you are
pushing the earth away from yourself with the same force
what would happen to the earth sun's gravity somehow turned off instantaneously - -it
would continue to move in the line in the same direction it was moving when the gravity
turned off
Newton's Universal Law of Gravitation - -This law gives the force of gravity between any
two objects in the Universe. The force of gravity is proportional to (mass of object 1) ×
(mass of object 2) divided by the distance between the two objects squared:
F M1 x M2 / d 2
Again, more mass = stronger gravity. If the objects were moved 2 times closer (or, to
half of their initial distance between), ...
F M1 x M2 / (1/2) 2 = M1 x M2 / (1/4) = 4 (M1 x M2)
... so, the gravitational attraction would become 4 times as great.
The Seasons, Day & Night - -Q: What causes day and night?
A: Rotation of the Earth on its axis.
ASTRO 7N
, ASTRO 7N
Q: How does the Sun appear to move in the sky in the course of a day?
A: East to West, because of Earth's rotation. The stars and planets move in the same
way from our point of view, also, because of Earth's rotation.
Q: What happens to the Earth in one year?
A: It orbits the Sun, once (also referred to as one complete revolution about the Sun).
Q: Why do we have seasons?
A: The tilt of the Earth's axis of rotation, with respect to the plane of its orbit around
the Sun (and not because of changing distance from Sun).
The Earth's tilt is about 23 degrees.
Q: How is the Earth's axis tilted when we have summer in the Northern hemisphere?
A: With the North pole toward the Sun.
Q: What season is it in the Southern hemisphere when it is summer in the
Northern hemisphere?
A: Winter
The Seasons, Day & Night pt2 - -Winter begins on or about Dec. 21 = in the Northern
hemisphere, the nights are longer than days
Spring begins on or about March 21 = days and nights have equal length
Summer begins on or about June 21 = days longer than nights in the North
Fall begins on or about Sept. 21 = days and nights have equal length
Seasons would not happen if the Earth's axis were not tilted. The distance between the
Earth and the Sun does not change very much over the course of a year, so the
temperature does not change much for that reason. Without the tilt of Earth's axis there
would be no seasons on Earth. Mars has a similar tilt to its rotation axis as Earth does.
if earth rotated on it axis more slowly than it does now; - -days would be longer
if earth had its orbit changed so that all points along its orbit it were always the same
distance from the sun (circular orbit), how would this affect the seasons on earth? - -
they would be the same as they are now
a new planet orbits its star faster than the earth orbits the sun and it rotates more slowly
than he earth rotates. which is true - -the new planet has a shorter year than earth and a
longer day than earth
what time of year is it dark all (and night) at the south pole of earth? - -June
ASTRO 7N
Astro 7N Revised Exam 1 2025
The force of gravity by the Sun keeps the planet in orbit around it, but how do the
planets affect the sun? - -They exert an equally strong pull on the sun, causing it move
slightly
Newton's First Law - -An object at rest stays at rest and an object in motion stays in
motion with the same speed and in the same direction unless acted upon by an
unbalanced force.
ex: if the sun suddenly disappeared, the Earth would continue in the direction that it was
traveling in its orbit at that time
Newton's Second Law - -The acceleration of a body due to a force will be in the same
direction as the force, with magnitude directly proportional to its mass
Force = mass x acceleration
A smaller mas will move faster, if the same force is applied to it
Newton's Third Law - -For every action there is an equal and opposite reaction
The Sun exerts force on planets, and they orbit it - he planets exert equal force on Sun,
but it only moves slightly because of its very large mass relative to the planets
Surface Gravity on a Planet - -the strength of gravity: g = m/r^2
Where M is the mass of the planet and R is its radius. Note the radius is squared but the
mass is not.
More mass = more gravity.
- If the mass of a planet were twice that of another, but they had the same radius, the
gravity felt on the surface of the more-massive one would be twice as strong.
Larger separation = less gravity.
- If the radius of a planet were twice that of another, the gravity is 1 / (2) 2 = 1/4 as
strong.
Putting the effects of mass and radius together, you should be able to figure out the
surface gravity of Mars, relative to the Earth.
- Mars has 1/10 the mass of the Earth and 1/2 the radius of Earth. So for Mars,
g = (1/10) / (1/2) 2 = (1/10) / (1/4) = 4/10
ASTRO 7N
,ASTRO 7N
Mars has a surface gravity 4/10 that of Earth. You will need to be able to do this type of
estimate for the test, given the numbers for mass and radius.
If I apply exactly the same amount of force to a pebble and a boulder, what will happen -
-the pebble will move faster
If the Earth were moved to half its current distance from the sun, how would the force of
gravity by the sun on the earth change? - -it would become 4 times weaker
Mass - -As the mass of the planet increases, the jump height does decreases by the
same factor
As the mass of the planet decreases, the jump height does increases by the same
factor
According to Newton's Second law of motion, if the net force acting on the object
increases while the mass of the object remains constant, what happens to acceleration -
-acceleration increases
If the earth were moves to half its current distance from the Sun, how would the force of
gravity by the Sun on the Earth change - -it would become four times weaker
What did newton's law of universal gravitation tell us about how gravity works - -the
force of gravity from the sun will be stronger on object with more mass
If you were to sit on the ground, there would be a force due to gravity pulling you toward
the earth. which of the following is true according to newton's third law - -you are
pushing the earth away from yourself with the same force
what would happen to the earth sun's gravity somehow turned off instantaneously - -it
would continue to move in the line in the same direction it was moving when the gravity
turned off
Newton's Universal Law of Gravitation - -This law gives the force of gravity between any
two objects in the Universe. The force of gravity is proportional to (mass of object 1) ×
(mass of object 2) divided by the distance between the two objects squared:
F M1 x M2 / d 2
Again, more mass = stronger gravity. If the objects were moved 2 times closer (or, to
half of their initial distance between), ...
F M1 x M2 / (1/2) 2 = M1 x M2 / (1/4) = 4 (M1 x M2)
... so, the gravitational attraction would become 4 times as great.
The Seasons, Day & Night - -Q: What causes day and night?
A: Rotation of the Earth on its axis.
ASTRO 7N
, ASTRO 7N
Q: How does the Sun appear to move in the sky in the course of a day?
A: East to West, because of Earth's rotation. The stars and planets move in the same
way from our point of view, also, because of Earth's rotation.
Q: What happens to the Earth in one year?
A: It orbits the Sun, once (also referred to as one complete revolution about the Sun).
Q: Why do we have seasons?
A: The tilt of the Earth's axis of rotation, with respect to the plane of its orbit around
the Sun (and not because of changing distance from Sun).
The Earth's tilt is about 23 degrees.
Q: How is the Earth's axis tilted when we have summer in the Northern hemisphere?
A: With the North pole toward the Sun.
Q: What season is it in the Southern hemisphere when it is summer in the
Northern hemisphere?
A: Winter
The Seasons, Day & Night pt2 - -Winter begins on or about Dec. 21 = in the Northern
hemisphere, the nights are longer than days
Spring begins on or about March 21 = days and nights have equal length
Summer begins on or about June 21 = days longer than nights in the North
Fall begins on or about Sept. 21 = days and nights have equal length
Seasons would not happen if the Earth's axis were not tilted. The distance between the
Earth and the Sun does not change very much over the course of a year, so the
temperature does not change much for that reason. Without the tilt of Earth's axis there
would be no seasons on Earth. Mars has a similar tilt to its rotation axis as Earth does.
if earth rotated on it axis more slowly than it does now; - -days would be longer
if earth had its orbit changed so that all points along its orbit it were always the same
distance from the sun (circular orbit), how would this affect the seasons on earth? - -
they would be the same as they are now
a new planet orbits its star faster than the earth orbits the sun and it rotates more slowly
than he earth rotates. which is true - -the new planet has a shorter year than earth and a
longer day than earth
what time of year is it dark all (and night) at the south pole of earth? - -June
ASTRO 7N
