A fragment of a collapsing gas cloud that comes to equilibrium with a central temperature of 4 million K will become a
A) T-Tauri star.
B) black dwarf.
C) black hole.
D) brown dwarf.
E) stage 1 protostar.
D
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Why do scientists describe the theory of gravity as "incomplete"?
A) It does not incorporate a description of matter on a very small scale. B) It does not explain why light bends near a dense object. C) It does not agree with the expansion of the universe. D) The gravity waves it predicts have not been observed. E) It does not explain the effects on time from a massive object.
A square coil (length of side = 24 cm) of wire consisting of two turns is placed in a uniform magnetic field that makes an angle of 60° with the plane of the coil. If the magnitude of this field increases by 6.0 mT every 10 ms, what is the magnitude of the emf induced in the coil?
a. 55 mV b. 46 mV c. 50 mV d. 60 mV e. 35 mV
A 2.5-kg box, sliding on a rough horizontal surface, has a speed of 1.2 m/s when it makes contact with a spring (see the figure)
The block comes to a momentary halt when the compression of the spring is 5.0 cm. The work done by the friction, from the instant the block makes contact with the spring until is comes to a momentary halt, is -0.50 J. (a) What is the spring constant of the spring? (b) What is the coefficient of kinetic friction between the box and the rough surface? What will be an ideal response?
A rocket takes off vertically from the launchpad with no initial velocity but a constant upward acceleration of 2.25 m/s2. At 15.4 s after blastoff, the engines fail completely so the only force on the rocket from then on is the pull of gravity
(a) What is the maximum height the rocket will reach above the launchpad? (b) How fast is the rocket moving at the instant before it crashes onto the launchpad? (c) How long after engine failure does it take for the rocket to crash onto the launchpad?