Slide 1

Two satellites A and B of the same mass are going around Earth in concentric orbits. The distance of satellite B from Earths center is twice that of satellite A. What is the ratio of the centripetal force acting on B to that acting on A ? 1. 1/8 2. 1/4 3. 1/2 4. 12 5. 1

Slide 2

Two satellites A and B of the same mass are going around Earth in concentric orbits. The distance of satellite B from Earths center is twice that of satellite A. What is the ratio of the tangential speed of B to that of A ? 1. 12 2. 12 3. 1 4. 2 5. 2

Slide 3

Suppose Earth had no atmosphere and a ball were fired from the top of Mt. Everest in a direction tangent to the ground. If the initial speed were high enough to cause the ball to travel in a circular trajectory around Earth, the balls acceleration would 1. be much less than g (because the ball doesnt fall to the ground). 2. be approximately g. 3. depend on the balls speed.

Slide 4

The Moon does not fall to Earth because 1. It is in Earths gravitational field. 2. The net force on it is zero. 3. It is beyond the main pull of Earths gravity. 4. It is being pulled by the Sun and planets as well as by Earth. 5. all of the above 6. none of the above

Slide 5

Black Holes What is a black hole? Gravitational well with extremely high gravitational forces. Singularity Event Horizon (Point of no return) RsRs Creation of a black hole: 1.Massive star explodes Supernova 2.Mass that does not travel far enough gets pulled back and the mass collapses under gravitational forces to form one of the following: a)White Dwarf M < 1.4 M sun b)Neutron Star M > 1.4 M sun c)Black Hole M > 3 M sun For a black hole the mass is compacted into a single point called a singularity. Ideally this point would have zero volume and therefore infinite density. Everything that enters a black hole (passes the event horizon) is pulled into the singularity, including light! R s Schwartzchild radius Extremely dense star (R ~ 10 km) 1 teaspoon weighs 5 billion tons!

Slide 6

The black hole can emits high energy electromagnetic radiation, as shown in the illustration below. This electromagnetic radiation is not in the visible spectrum. A star loses mass to a black hole. This is the result of a single star of a binary pair collapsing into a black hole, or possibly a single star exploding and creating a black hole and another star. An astronaut entering a black hole. The gravitational forces are so strong that the gravitational force at the astronauts head is stronger than the gravitational force at his feet. This causes the stretching and eventually the astronaut would be torn apart.