Ch 3

Kepler's 1st Law

Each planet moves around the Sun in an orbit that is an ellipse, with the Sun at one focus of the ellipse.

a^3=(M1+M2)×P^2

Equation for the relationship between the orbital period of a planet's revolution and its distance from the Sun.

Newton's 1st Law

Every object will continue to be in a state of rest or move at a constant speed in a straight line unless it is compelled to change by an outside force.

Newton's 3rd Law

For every action there is an equal and opposite reaction (or: the mutual actions of two bodies upon each other are always equal and act in opposite directions).

9 times weaker

How does the gravitational force change when the distance between two objects is tripled?

Mathematicians used Newton's Laws and measurements of Uranus.

How was Neptune discovered?

P^2=a^3

Kepler's Third Law equation for solving the period.

Density

Mass divided by volume

Conservation of Momentum

Momentum can be transferred from one object to another

To get from Mars back to Earth, you'd have to take a huge rocket with you, which would require enormous amounts of fuel

You are looking at NASA mission proposals to Mars. Why is a sample return mission so much more expensive than a flyby mission?

True

True or False: Since all the planets orbit the Sun, the Sun's mass is the same for all the planets in Kepler's third law. The individual masses for each of the planets are so small compared to the Sun that they are insignificant in calculating and can be treated as if they were zero and not significantly change the answer.

Momentum

depends on three factors: (1) speed—how fast a body moves (zero if it is stationary), (2) the direction of its motion, and (3) its mass—a measure of the amount of matter in a body

Newton's law of gravitation

-Every mass attracts (exerts a force) every other mass -The force is directly proportional to the product of their masses -The force is inversely proportional to the square of the distance between them

Speed

-How fast something is moving -s=d/t

Momentum

-How had it is to stop something

Kepler's 1st Law

-Orbits are ellipses with the sun at one focus -Ellipse size is determined by the semi-major axis (a) -Ellipse shape is determined by eccentricity (e)

Force

-Push or pull -causes acceleration

Fastest, Slowest

According to Kepler's second law, where in a planet's orbit would it be moving fastest? Where would it be moving slowest? The planet would move ____ when it is closest to the Sun (at perihelion) ____ when farthest from the Sun (at aphelion).

Conservation of Angular Momentum

As a planet approaches the Sun on its elliptical orbit and the distance to the rotation center decreases, the planet speeds up to conserve the angular momentum. Similarly, when the planet is farther from the Sun, it moves more slowly

Acceleration

Change in speed

Newton's 2nd Law

The change of motion of a body is proportional to and in the direction of the force acting on it.

Fgravity=G(M1M2/R2)

The gravitational attraction between any two objects.

Orbit

The path of an object through space.

Fastest, Slowest

The planet would move______when it is closest to the Sun (at perihelion) and ______ when farthest from the Sun (at aphelion).

Kepler's Third Law

The square of a planet's orbital period is directly proportional to the cube of the semi major axis of its orbit.

Kepler's Second Law

The straight line joining a planet and the Sun sweeps out equal areas in space in equal intervals of time.

Inertia

The tendency of objects to keep doing what they are already doing. In other words, a stationary object stays put, and a moving object keeps moving unless some force intervenes.

Mass

a measure of the amount of material within an object

Velocity

speed and direction

Volume

the measure of the physical space it occupies

Acceleration

the rate of change in an object's velocity