Explain why the passing star hypothesis was problematic
What will be an ideal response?
First, stars are very far apart in relation to their sizes and their relative velocities, so they collide very infrequently. Only a tiny fraction of stars in our Galaxy have ever suffered a collision or close encounter with another star. Also, the gas pulled from the Sun and the star would be much too hot to condense to make planets, and it would have dispersed instead. Furthermore, even if planets did form from that gas, they would not have gone into stable orbits around the Sun.
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A 2.0-?F capacitor in series with a 2.0-k? resistor is connected to a 60-Hz ac source. Calculate the impedance of the circuit
a. 1 500 ohms b. 1 800 ohms c. 2 100 ohms d. 2 400 ohms e. 8 600 ohms
A jogger is running outdoors on a cold day when the temperature is -20.0°C. Each time she breathes, she inhales 0.00450 m3 of air
She is breathing at the rate of 25 breaths per minute. How much heat does she lose from breathing during 20.0 minutes of jogging if the air in her lungs is heated to body temperature (37°C) before it is exhaled? The specific heat of air is 1020 J/(kg?K) and the density of air is 1.29 kg/m3. A) 169 kJ B) 278 kJ C) 354 kJ D) 431 kJ E) 543 kJ
You lift a book with your hand in such a way that it moves up at constant speed. While it is moving, what is the total work done on the book?
a) mg × ?r b) FHAND × ?r c) (FHAND + mg) × ?r d) zero e) none of the above
An object moving with speed 
collides head-on with an object at rest that is very much more massive. If the collision is elastic, how does the lighter object’s speed 
after collision compare to ?
A. 
B. 
C. 
D. 
E. 
F. 