Multiple Choice
Passage
Black holes have played an important part in astrophysics for the last half-century. A black hole is a region of space where the force of gravity is especially strong and gravitational potential energy U is very large. Analogous to the electrostatic potential energy associated with electrical charges, U is defined as the work required to move an object of mass m from an infinite distance to a point at radial distance r within the gravitational field of a second mass M as given by
Equation 1where G is the gravitational constant. Near a black hole, the gravitational potential energy can become so negative that not even light has enough energy to escape the black hole's gravity.Escape velocity can be determined by launching an object of mass m with velocity v to an infinite radial distance from the surface of a central mass M (eg, a star or a planet) with radius R. For a black hole to exist, the escape velocity must be equal to the speed of light.Scientists have thoroughly studied the physics of black holes. Stars near the center of our galaxy have been observed to orbit an extremely massive, invisible object (millions of times more massive than our Sun) that is almost certainly a black hole. The orbital angular velocity ω of a star is defined as
ω=360°⋅fEquation 2where f is the frequency of rotation in hertz (Hz) . Likewise, black holes are not merely static masses but are often observed to rotate about their own axis. The interaction between the rotation of a black hole and matter falling into the hole is suspected to form powerful beams (jets) of ionized matter that project away from the black hole along its axis of rotation. Nevertheless, many aspects of how these jets are formed remains a mystery. Black holes will remain a fruitful area for research far into the future.
-An object is launched with a one-time burst of propulsion away from the surface of a planet with no atmosphere. Which of the following best describes the changes that occur as the object moves away from the planet's surface?
A) The object mass is dissipated as heat.
B) Potential energy is converted into kinetic energy.
C) Kinetic energy is converted into potential energy.
D) Total mechanical energy is not conserved.
Correct Answer:

Verified
Correct Answer:
Verified
Q154: Passage<br>Nitrogen is extremely cold in its liquid
Q155: A 100-g block of iron at 31°C
Q156: A cube with a side length of
Q157: Passage<br>In the event of end-stage heart failure,
Q158: Passage<br>A student performed an experiment to determine
Q160: Passage<br>Sound waves propagate through many conducting structures
Q161: A scientist studying capillary fluid exchange in
Q162: Passage<br>Osteoporosis is a degenerative bone condition in
Q163: <img src="https://d2lvgg3v3hfg70.cloudfront.net/MD0008/.jpg" alt=" A 4-μF capacitor
Q164: Which of the following procedures best describes