Ch. 13 Gravitational Interactions

Gravitational Field

Does the gravitational field exist inside of a planet?????

Does the gravitational field exist inside of a planet?????

• Yes!!!

The force of Gravity, like other forces, causes acceleration!

• How does this relate to weight?

The force of Gravity, like other forces, causes acceleration!

• How does this relate to weight?• How does this relate to weightlessness?

Support Force plays a factor in our concept of weight

Gravity at work on Earth!Ocean tides • caused by differences in the gravitational pull

of the moon on opposite sides of the Earth. – Pull is stronger when the moon is closer and

weaker when it is further away.

• Spring Tide

Black Holes

• Stars– Fusion reactions (H He )– Leading to increased mass and thus increased

gravitational force!

– When a star runs out of hydrogen, the star begins to cool and collapse, allowing a second fusion reaction to occur (He C)

– This will lead to another expansion of the star (Red Giant phase)

– When the helium is all used up, the Red Giant will collapse. (Black Dwarf)

• Black Holes: For stars 2-3 x bigger than the sun, once nuclear fusion stops, gravity takes over and it doesn’t stop! The star caves in on itself and the density inside is infinite. – Not even light can escape.

The biggest black hole in the universe weighs in with a mass of 18 billion Suns, and is about the size of an entire galaxy!

• Mass of a black hole = mass of the star that it originated from– Gravitational field of the star and the black hole at

distances greater than the original radius of the star are the same!

• F = Gm/d2

– As distance approaches zero, Force of gravity is approaching infinity

• Diagram of the gravitational field around a black hole.

• The center has the strongest force but at distances further away, the field is stable.

• The End