Gravity Basics
What is gravity?
A pulling force that attracts all objects with mass toward each other.
What is the difference between mass and weight?
Mass = amount of matter (never changes, kg). Weight = gravitational force on that mass (changes by location, measured in N)
An orbit is the result of two things working together. Name both.
Gravity (pulling inward) AND the object maintaining enough velocity/sideways inertia (keeping the object moving forward).
The pathway around another object
Orbit
The time it takes for one full revolution around another celestial body.
Orbital Period
What 3 things affect the gravity between objects?
Distance between the objects and the Mass of each object and the radius
What unit is weight measured in?
Newtons (N)
What would happen to a satellite if it suddenly slowed down?
Gravity would win — the satellite would spiral inward toward Earth (and could crash).
What shape are all planetary orbits?
An ellipse (not a perfect circle!).
Minimum speed needed for an object to escape the gravity of a planet and leave orbit.
Escape Velocity
If the distance between two objects increases, the gravitational force will do what?
Decrease (get smaller)
A student has a mass of 70 kg. What is her mass on the Moon?
70 kg — mass never changes, no matter where you are!
* DAILY DOUBLE *
Why do astronauts on the International Space Station appear to float even though gravity is pulling on them?
They are in free fall b/c their velocity and gravity are balanced — they and the ISS fall together, so there is no normal force.
Minimum Speed needed for a body to keep moving forward around a planet but not be pulled to that planet.
Orbital Velocity
List the 3 types of galaxies.
Spiral, Elliptical, and Irregular
This variable affects gravitational pull on the planet. As it gets larger, we get further from the core/center, and the gravitational pull gets smaller.
Radius
Type of matter that has mass and gravitational pull but is invisible.
Dark Matter
What is Earth's orbital period?
Pathway of an object through air or space?
Trajectory
This type of galaxy is shaped like a disc and its arms revolve in the same around the center. This is the type of galaxy we live in.
A Spiral Galaxy - the Milky Way is an example of one and is where we live.
Why does the black hole in the center of the milky way, which is much larger than our sun, not pull us into it?
Because it is too far away. The extreme distance overrides the mass of the black hole.
How do we know dark matter exists if we can't see it? (Think about the mystery tubes)
Explain how scientists can tell the approximate age of distant galaxies.
As galaxies move away from us, the wavelength of their light stretches and shifts towards the RED end of the spectrum ----ROYGBIV
Average distance between the sun and the earth?
Astronomical Unit
Which type of galaxy has no definite shape and seems to be pulled by other galaxies?
Irregular Galaxy.