ASTRO 7N UPDATED ACTUAL QUESTIONS
AND CORRECT ANSWERS COMPLETE
STUDY GUIDE
●● Newton's First Law
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
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
A smaller mas will move faster, if the same force is applied to it
●● Newton's Third Law
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
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.
- 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
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?
Answer: it would become 4 times weaker
●● Mass
Answer: 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
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
Answer: it would become four times weaker
●● What did newton's law of universal gravitation tell us about how
gravity works
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
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
Answer: 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
Answer: 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) ×
AND CORRECT ANSWERS COMPLETE
STUDY GUIDE
●● Newton's First Law
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
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
A smaller mas will move faster, if the same force is applied to it
●● Newton's Third Law
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
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.
- 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
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?
Answer: it would become 4 times weaker
●● Mass
Answer: 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
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
Answer: it would become four times weaker
●● What did newton's law of universal gravitation tell us about how
gravity works
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
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
Answer: 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
Answer: 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) ×
