Astro 7N Exam 1 2026 Questions and
Answers Graded A+
The force of gravity by the Sun keeps the planet in orbit around it, but how do the
planets affect the sun? - Correct answer-They exert an equally strong pull on the
sun, causing it move slightly
Newton's First Law - Correct answer-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 - Correct answer-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
©COPYRIGHT 2026, ALL RIGHTS RESERVED 1
,A smaller mas will move faster, if the same force is applied to it
Newton's Third Law - Correct answer-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 - Correct answer-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.
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,- 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
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 - Correct answer-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? - Correct answer-it would become
4 times weaker
Mass - Correct answer-As the mass of the planet increases, the jump height does
decreases by the same factor
©COPYRIGHT 2026, ALL RIGHTS RESERVED 3
, 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 - Correct answer-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 - Correct answer-it would become
four times weaker
What did newton's law of universal gravitation tell us about how gravity works -
Correct answer-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 -
Correct answer-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 -
Correct answer-it would continue to move in the line in the same direction it was
moving when the gravity turned off
©COPYRIGHT 2026, ALL RIGHTS RESERVED 4
Answers Graded A+
The force of gravity by the Sun keeps the planet in orbit around it, but how do the
planets affect the sun? - Correct answer-They exert an equally strong pull on the
sun, causing it move slightly
Newton's First Law - Correct answer-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 - Correct answer-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
©COPYRIGHT 2026, ALL RIGHTS RESERVED 1
,A smaller mas will move faster, if the same force is applied to it
Newton's Third Law - Correct answer-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 - Correct answer-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.
©COPYRIGHT 2026, ALL RIGHTS RESERVED 2
,- 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
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 - Correct answer-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? - Correct answer-it would become
4 times weaker
Mass - Correct answer-As the mass of the planet increases, the jump height does
decreases by the same factor
©COPYRIGHT 2026, ALL RIGHTS RESERVED 3
, 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 - Correct answer-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 - Correct answer-it would become
four times weaker
What did newton's law of universal gravitation tell us about how gravity works -
Correct answer-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 -
Correct answer-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 -
Correct answer-it would continue to move in the line in the same direction it was
moving when the gravity turned off
©COPYRIGHT 2026, ALL RIGHTS RESERVED 4
