Astronomers can measure a star's mass in only certain cases. Which one of the following cases might allow astronomers to measure a star's mass?
A) The star is a member of a binary star system.
B) The star is of spectral type G.
C) The star is of spectral type A.
D) We know the star's luminosity and distance.
A) The star is a member of a binary star system.
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Two 0.20-kg balls, moving at 4 m/s east, strike a wall. Ball A bounces backwards at the same speed. Ball B stops. Which statement correctly describes the change in momentum of the two balls?
A.
.B.
.C.
.D.
.E.
.Bulk Modulus: A 5000-N force compresses a steel block by 0.0025 cm. How much force, applied over the same area, would be needed to compress the block by 0.0125 cm?
A. 1000 N B. 2500 N C. 5000 N D. 25,000 N
What two quantities did Edwin Hubble compare for a sample of galaxies to discover the expansion of the universe?
A) velocity and distance B) luminosity and distance C) velocity and temperature D) luminosity and temperature E) age and distance
A slide projector needs to focus the image of a 24.0-mm × 36.0-mm slide onto a square screen 1.50 m on each side. You want to fill the screen as completely as possible without any of the image falling beyond the screen
Due to space constraints in the projector, the slide must be placed 10.5 cm from the lens. (a) What magnification does the projector produce? (b) How far from the lens should the screen be placed? (c) What focal length projector lens is needed?