Redshift surveys give us
A) a 3-D layout of galaxies in space.
B) a better value of the speed of light.
C) an idea of how turbulent the intergalactic gas is.
D) the total mass of the universe.
E) a more accurate census of the Local Group.
A
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Shake an object to and fro if you want to judge its
A) mass. B) weight. C) both the same D) none of the above
A runaway railroad car, with mass 45.0 × 10^4 kg, coasts across a level track at 3.80 m/s when it collides with a spring-loaded bumper at the end of the track. If the spring constant of the bumper is 3.80 × 10^6 N/m, what is the maximum compression of the spring during the collision? (Assume the collision is elastic.)
a. 1.31 m b. 1.85 m c. 0.925 m d. 2.10 m e. 2.62 m
A submarine is at a depth of 500 m under the water. The force on a circular hatch of 1.00 m in diameter due to the seawater 
pressure from outside the submarine is
A. 
B. 
C. 
D. 
E. 
A horizontal disk 1 m in diameter rotates in air at 25°C. If the disk is at 100°C, estimate the number of revolutions per minute at which natural convection for a stationary disk becomes less than 10% of the heat transfer for a rotating disk.
GIVEN
? A rotating horizontal disk in air
? Diameter (D) = 1 m
? Air temperature (T?) = 25°C
? Disk temperature (Ts) = 100°C
FIND
? The rotational speed (w) at which natural convection becomes less than 10% of the thermal effects
of rotation
ASSUMPTIONS
? Steady state conditions
SKETCH
PROPERTIES AND CONSTANTS
From Appendix 2, Table 28, for dry air at the mean temperature of 62.5°C
