What is the best way to determine a galaxy's redshift?
A) Find the galaxy's apparent distance, and look up the redshift based on Hubble's Law.
B) Find the color of the galaxy, and estimate its distance based on how red the galaxy is.
C) Measure the magnitude of the galaxy, estimate its distance, and calculate its redshift using Hubble's Law.
D) Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory.
D
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An object with mass m and moment of inertia I is spinning with an angular momentum L. Its kinetic energy is:
a. 0.5I2/L. b. 0.5L2/I. c. 0.5L2/m. d. 0.5I2/m.
Engine oil flows at a rate of 0.5 kg/s through a 2.5-cm-ID tube. The oil enters 25°C while the tube wall is at 100°C. (a) If the tube is 4-m-long. Determine whether the flow is fully developed. (b) Calculate the heat transfer coefficient.
GIVEN
• Engine oil flows through a tube
• Mass flow rate (m
) = 0.5 kg/s
• Inside diameter (D) = 2.5 cm = 0.025 m
• Oil temperature at entrance (Ti) = 25°C
• Tube surface temperature (Ts) = 100°C
• Tube length (L) = 4 m
FIND
(a) Is flow fully developed? (b) The heat transfer coefficient (hc) ASSUMPTIONS
• Steady state
SKETCH
Which of the following statements about an ellipse is not true?
A) The semimajor axis of an ellipse is half the length of the longest line that you can draw across an ellipse. B) An ellipse with a large eccentricity looks much more elongated (stretched out) than an ellipse with a small eccentricity. C) A circle is considered to be a special type of ellipse. D) The focus of an ellipse is always located precisely at the center of the ellipse.
A ball is thrown vertically upward with an initial speed of 20 m/s. Two seconds later, a stone is thrown vertically (from the same initial height as the ball) with an initial speed of 24 m/s. At what height above the release point will the ball and stone pass each other?
a. 17 m b. 21 m c. 18 m d. 27 m e. 31 m