A typical protostar may be several thousand times more luminous than our Sun. Where does this energy come from?
What will be an ideal response?
From the release of gravitational energy as the protostar shrinks in stages 2 and 3.
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A vertical spring is compressed and when released applies a force during a 0.25 s time interval to a 17 g frog, which is flung upward due to the applied force from the spring. If the frog attains a velocity of 11 m/s after being released from the spring, what average force was applied by the spring?
A. 0.21 N B. 0.91 N C. 0.75 N D. 0.17 N E. 0.58 N
Kepler's Third law relates a planet's orbital period and its average distance from the Sun (p2 = a3 ). If a new comet were discovered with an average distance from the Sun of 100 AU, its period would be
A) 1000 years. B) 10,000 years. C) 150 years. D) 1 million years. E) not enough information to say.
A ray of light enters an equilateral prism made of material with n = 1.45. What angle of incidence, 
will cause the internally refracted ray to be parallel to the base of the prism?
A. 46.5 
B. 30.0
C. 20.2 
D. 5.70
E. this cannot happen
Equal but opposite charges Q are placed on the square plates of an air-filled parallel-plate capacitor
The plates are then pulled apart to twice their original separation, which is small compared to the dimensions of the plates. Which of the following statements about this capacitor are true? (There may be more than one correct choice.) A) The energy stored in the capacitor has doubled. B) The energy density in the capacitor has increased. C) The electric field between the plates has increased. D) The potential difference across the plates has doubled. E) The capacitance has doubled.