Astro 7N Unit 1 Flashcards
What is Newton’s First Law?
An object at rest, or in motion in a straight line at a constant speed, will remain in that state unless acted upon by a force.
What is Newton’s Second Law?
acceleration due to a force will be in the same direction as the force, with a magnitude inversely proportional to its mass
What is Newton’s Third Law?
For every action, there is an equal and opposite reaction
What is an example of Newton’s First Law?
If the Sun suddenly disappeared, the Earth would continue in the
direction that it was traveling in its orbit at that time
What is the equation for Newton’s Second Law?
Force = mass x acceleration
What is an example of Newton’s First Law?
A smaller mass will move faster, if the same force is applied to it
What is an example of Newton’s Third Law?
The Sun exerts force on planets, and they orbit it — the planets exert equal force on Sun, but it only moves slightly because of its very large mass relative to the planets
What is the gravity strength equation?
g = M / R^2, m is mass and r is radius
What is the correlation between mass and gravity?
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
What is the correlation between separation and gravity?
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
What is the surface gravity of Mars relative to 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
What is Newton’s Universal Law of Gravitation?
force of gravity between any two objects in the Universe. 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
Based off the Universal Law of Gravitation, what would the force be if objects were moved two times closer?
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
What causes day and night?
Rotation of the Earth on its axis.
How does the Sun appear to move in the sky in the course of a day?
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.
What happens to the Earth in one year?
It orbits the Sun, once (also referred to as one complete revolution about the Sun).
Why do we have seasons?
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.
How is the Earth’s axis tilted when we have summer in the Northern hemisphere?
With the North pole toward the Sun.
What season is it in the Southern hemisphere when it is summer in the Northern hemisphere?
Winter
Winter begins on or about Dec. 2, which is when
in the Northern hemisphere, the
nights are longer than days
Spring begins on or about March 21, which is when
days and nights have equal length
Summer begins on or about June 21, which is when
days longer than nights in the North
Fall begins on or about Sept. 21, which is when
days and nights have equal length
Would seasons happen even if the Earth’s axis was 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
