If a neutral element has the following chemical symbol, how many electrons does it have?
ImageU
A) 92
B) 82
C) 235
D) 143
E) none of the above
Answer: A
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Consider two blinking warning lights 3000 m apart along a railroad track. These lights flash simultaneously in the ground frame. Let W be the event of the west light blinking, and let E be the event of the east light blinking. A train moves eastward along the track at a relativistic speed ?. Suppose an observer in the train passes the west light just as event W happens. By carefully measuring when the light from event E arrives and calculating the distance between the two lights (by observing how long it takes to travel between the lights at the known speed ?), the observer is able to infer when event E actually happened in the train frame. The observer concludes that
A. Event W happened before event E in the train frame. B. Events W and E were simultaneous in the train frame. C. Event E happened before event W in the train frame. D. One cannot determine unambiguously which event occurs first in the train frame.
What factor caused different planets to form out of different types of material?
A) The angular momentum of the forming planet; faster rotating planets lost the lightest elements. B) The quantity of dust particles in the solar nebula; more dust caused some planets to contain heavier elements. C) The variation in temperature throughout the solar nebula; the higher the temperature, the lower the percentage of light elements in the forming planet. D) The angular momentum of the solar nebula pushed the heavy elements towards the outer regions of the nebula. E) The innate variation of chemical composition of the original nebula; the outer parts of the nebula contained a greater abundance of heavy elements.
In the context of star clusters, which of the following statements is true of the turnoff point?
A) It is the point on the main sequence of a Hertzsprung-Russell diagram that is used to determine the luminosity class of the stars in the cluster. B) Stars at this point are considered to have just taken birth and have 90 percent of their life remaining. C) The life expectancy of the stars at this point is not equivalent to the age of the cluster. D) It is the point on the main sequence of a Hertzsprung-Russell diagram where stars evolve to the right of the H-R diagram to become giants.
A roller coaster car (mass = M) is on a track that forms a circular loop (radius = r) in the vertical plane. If the car is to just maintain contact with the track at the top of the loop, what is the minimum value for its speed at that point?
A) rg B) 2rg C) (rg)1/2 D) (2rg)1/2 E) (0.5rg)1/2