Gravity

Gravity

King City Astronomy 1Class 2

Zoe Buck

The Most Important Things about GRAVITY

• Gravity is what makes things fall toward the Earth (not “down”, but “toward the Earth”)

• Gravity is a force between two objects• How much gravity something exerts is based

exclusively on its MASS• Gravity keeps things in orbit (Satellites, Moon,

Earth, Sun)• The force of gravity between two objects can be

determined using the formula F= G(m*M)/r²• Gravity drives the formation of galaxy clusters,

galaxies, stars, and planetary systems• Gravity determines the structure of the Universe

• Acceleration: a change in the velocity of an object

• Force: something that causes an acceleration

Newton’s Laws

1. An object’s velocity will not change unless acted on by an external force

2. Force on an object is determined by the acceleration of the object, and the mass of that object (F=ma)

2. Every action has an equal and opposite reaction

Gravity depends on MASS

Acceleration of Gravity

Fg= m * a

Where M is the mass of the person or object, and a is the acceleration due to gravity, which we call g (“little g”)

On the surface of Earth, g is always the same. This means that when something falls on Earth, no matter WHAT IT WEIGHS, it accelerates at the same speed, so everything falls at the same rate.

Gravity depends on DISTANCE

• F = m * a• Fg

= m * g

• g=(G*M)/r² • (where G = G= 6.67 *10-11 N(m/kg)²)• Don’t confuse “little g” with “big G”

Gravity

• The UNIVERSAL LAW OF GRAVITATION

• Fg= m * g

• g=(G*M)/r² • (where G = G= 6.67 *10-11 N(m/kg)²)• So… Fg

= (G * M * m)/ r²

Newton and the Apple

Free Fall

Is there gravity in space?

• Zero Gravity DOESN’T EXIST!

• Microgravity

Free Fall + Velocity = Orbit

Gravity and the Universe

• Gravity is responsible for holding the Earth in its orbit around the Sun


• Gravity is responsible for holding the Sun in its orbit around the Milky Way


• Gravity is responsible for holding the Milky Way in its path within the Local Group


• Gravity is responsible for holding the Earth in its orbit around the Sun, the Sun in its orbit around the Milky Way, and the Milky Way in its path within the Local Group…it is the force that dictates the structure of the Universe

Gravity makes stars and galaxies

The Most Important Things about GRAVITY

• Gravity is what makes things fall toward the Earth (not “down”, but “toward the Earth”)

• Gravity is a force between two objects• How much gravity something exerts is based

exclusively on its MASS• Gravity keeps things in orbit (Satellites, Moon,

Earth, Sun)• The force of gravity between two objects can be

determined using the formula F= G(m*M)/r²• Gravity drives the formation of galaxy clusters,

galaxies, stars, and planetary systems• Gravity determines the structure of the Universe

Documents

Gravity