MEASURES & METHODS, MAGNITUDES & DISTANCES ------------------------------------------ The expression "order of magnitude" corresponds to $a) one factor of ten b) one factor of two c) a factor of 2.5 d) two factors of ten You are deciding which computer to buy, based on how long it takes to start running your favorite computer game. Which computer starts your game program the most quickly? a) Game starts in 1 centisecond b) Game starts in 1 kilosecond $c) Game starts in 1 microsecond d) Game starts in 1 millisecond e) Game starts in 1 second Multiplying together two numbers N*10^x and M*10^y in scientific notation yields the following, again in scientific notation a) (N*x) * 10^(M*y) b) (N+M) * 10^(x+y) c) (N*M) * 10^(x*y) $d) (N*M) * 10^(x+y) What do you get when you multiply 10 to the third power by 10 to the third power? a) 0 b) 1 over 10 to the third c) 10 to the ninth $d) 10 to the sixth e) 2 times 10 to the third At the start of the 21st century, the number of human beings alive on Earth was approximately a) 6 to the 9th power b) 6 to the 9th power of ten c) 6 times ten to the 9th power d) 6,000 million $e) both c and d The density of an object is its a) length divided by its width b) mass divided by its length and width $c) mass divided by its volume d) mass multiplied by its volume e) volume divided by its mass A gram of lead has a greater ______ than a gram of feathers. a) mass $b) density c) weight d) volume Say you need to multiply together measurements of differing precision, some with more significant figures than others. For example, the product of 7.00 * 6.1 is properly written as a) 42.70 $b) 42.7 c) 43 d) 43.0 Say you want to add measurements of differing precision, some with larger uncertainties than others, such as the sum 4.371 (+/- 0.001) cm + 302.5cm (+/- 0.1). This sum is correctly written as a) 306.001 cm b) 306.872 cm $c) 306.9 cm d) 307 cm You are parked on an asteroid watching spaceship traffic. You measure the velocity of a spaceship moving away from you to be +50 km/sec. A different spaceship approaches you at the same speed. In the same coordinate system, what velocity do you measure? a) +50 km/sec $b) -50 km/sec c) the velocities cancel to 0km/sec d) +100 km/sec The Angstrom unit is most suitable for describing a measurement of a) the distance between the Earth and the Sun b) any tiny angle $c) the wavelength of visible light d) the speed of light A bolt of lightning lasting one second imparts 100 million joules of energy to the square tip of an antenna that is 1 centimeter on a side. Down the street, an identical lightning bolt hits a square car roof that is 1 meter on a side. The flux (energy) passing through the antenna, compared to that passing through the car roof, is a) identical (lower) b) identical (higher) c) lower (identical) $d) higher (identical) e) higher (lower) Distance: -------- Sound travels at a speed of 300 meters per second. In analogy to the light-year, what does 1 sound-minute equal? a) The time sound takes to travel 300 meters. b) The time delay of a sound heard 300 meters away. $c) The distance traveled by sound in 1 minute. d) The speed of sound 1 minute later. The star Betelgeuse is about 500 light years away from us in the constellation Orion. If this star underwent a supernova explosion right now, approximately how long would it be until we found out about it? a) almost immediately b) 8 minutes c) 10 years $d) 500 years e) 500 light years If the speed of light were half what it is now, then a light year would a) take half as long to traverse at light speed $b) take the same amount of time to traverse at light speed c) last twice as many months d) last half as many months How far from the Earth is the nearest star? $a) 1 astronomical unit. b) 1 light year. c) 1 parsec. d) 10 light years. e) 10 parsecs. The trigonometric sine of a small angle between 2 points on a sphere is approximately equal to the linear separation between those points divided by a) the distance to the points b) the radius of the sphere c) the circumference of the sphere d) pi $e) a and b above The distances of nearer stars may be measured by observing their apparent motion as $a) the Earth orbits around the Sun b) the Earth rotates on its axis c) the Sun orbits around the center of the Galaxy d) the planets cross their path The most important reason for measuring the parallax of a star is to help us find the stars' a) direction of motion b) proper motion $c) intrinsic brightness (absolute magnitude) d) radial velocity If the parallax of a star is measured to be 0.1 seconds of arc, its distance is a) 10 astronomical units $b) 10 parsecs c) 1 parsec d) 0.1 parsec e) 0.1 astronomical units Two identical stars, one 5 light years from Earth, and a second 50 light years from Earth are discovered. How much fainter does the farther star appear to be? a) square root of 10 b) 10 $c) 100 d) 1,000 e) the farther star does not appear fainter, since it is identical Suppose that you have observed an asteroid over a month. You observe that it is now 25 times fainter than it was on the first day. Estimate how much farther away is it from you now than it was on the first day: a) twice as far $b) five times farther c) 12.5 times farther d) 25 times farther e) 625 times farther Star A is twice as far away as Star B, but they have the same luminosity. This means Star B has ____ times the flux of Star A. a) 1 b) 1/2 c) 1/4 d) 2 $e) 4 You photograph a region of the night sky in March, in September, and again the following March. The two March photos look the same, but the September photo shows three stars in different locations. The star whose position shifts the most must be a) farthest away. $b) closest. c) receding from Earth most rapidly. d) just passing through the Galaxy. What would you need to observe to find out the distance to a star that was too far away for trigonometric parallax? a) apparent brightness and intrinsic brightness (luminosity). b) apparent brightness and temperature. d) intrinsic brightness and temperature. $e) apparent brightness, spectral type, and luminosity. From Earth, planet A subtends an angle of 5 arcseconds, and planet B subtends an angle of 10 arcseconds. If the radius of planet A equals the radius of planet B, a) planet A is twice as big as planet B $b) planet A is twice as far as planet B c) planet A is half as far as planet B d) planet A and planet B are the same distance e) planet A is five times as far as planet B For two stars of the same apparent brightness, the star closer to the Sun will generally have a) a higher flux b) a hotter temperature $c) a lower luminosity e) identical physical properties If two intrinsically identical stars are at different distances from the Earth, the more distant star will have a a) bluer color. b) higher luminosity. $c) lower apparent flux. d) lower luminosity. Magnitude: --------- Using the magnitude system of astronomy, how would the brightness of an 8th magnitude star compare to a 7th magnitude star? a) 10 times brighter than the 7th magnitude sta b) 10 times dimmer than the 7th magnitude sta c) 2.5 times brighter than the 7th magnitude sta $d) 2.5 times dimmer than the 7th magnitude star. Four stars are all members of the same star cluster. They have the following absolute magnitudes, 10, 7, -1, -10. Which star appears brightest at the Earth? a) the first $b) the fourth c) the second d) the third The reason astronomers use the concept of the absolute magnitude is to allow stars to be compared directly removing the effects of differing $a) distance b) mass c) temperature d) radius The formula m-M = 5 logd -5 would not be true were it not for a) the fact that distance in parsecs is the reciprocal of the parallax in arcsec. b) Newton's Law of Gravitation. $c) the inverse square law or radiation. d) the definition of Vega as zero on the magnitude scale. Astronomical methods: -------------------- Images (or photographs) can be used to measure what properties of a star? a) Location on the sky. b) Distance. c) Brightness. d) Proper motion. $e) All of the above. Astronomers determine the `color' of a star by calculating the $a) ratio of the fluxes as measured with two different filters b) difference between the fluxes as measured with two different filters c) ratio of the temperature to the radius d) ratio of the absolute and the apparent brightnesses e) difference between the absolute and the apparent brightnesses The color of a star is a number representing the a) ratio of absolute luminosities at 2 wavelengths b) ratio of apparent luminosities (flux) at 2 wavelengths c) ratio of the star's area to its distance squared $d) Two choices are correct e) None of the choices is correct