Kim is in a spaceship moving past you at half the speed of light. Which of the following correctly describes how you will perceive each other's time?
A) You will say that Kim's time is running slow, and she will say that your time is running fast.
B) You will say that Kim's time is running slow, and she will say that your time is running slow.
C) You will say that Kim's time is running fast, and she will say that your time is running slow.
D) You will both agree that time runs at the same rate for both of you.
B
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Radioactive Decay: Isotope A has a decay constant of 0.723 s-1 and isotope B has a decay constant of 0.514 s-1. Which isotope has a longer half-life?
A. isotope A B. isotope B
which of the following stages will the sun definitely go through as it gets older?
What will be an ideal response?
In a manufacturing process, a fluid is transported through a cellar maintained at a temperature of 300 K. The fluid is contained in a pipe having an external diameter of 0.4 m and whose surface has an emissivity of 0.5. To reduce heat losses, the pipe is surrounded by a thin shielding pipe having an ID of 0.5 m and an emissivity of 0.3. The space between the two pipes is effectively evacuated to minimize heat losses and the inside pipe is at a temperature of 550 K. (a) Estimate the heat loss from the liquid per meter length, (b) If the fluid inside the pipe is an oil flowing at a velocity of 1 m/s, calculate the length of pipe for a temperature drop of 1 K.
GIVEN
- Fluid in concentric pipes, with the space between the pipes evacuated, running through a cellar space
- Cellar temperature (T?) = 300 K
- External diameter of inner pipe (D1) = 0.4 m
- Emissivity of outer pipe surface (?1) = 0.5
- Inside diameter of outer pipe (D2) = 0.5 m
- Emissivity of inner pipe (?2) = 0.3
- Inside pipe temperature (T1) = 550 K
FIND
(a) The heat loss from the liquid per meter length (q/L)
(b) The length of pipe for a temperature drop of 1 K if the fluid is oil flowing at a velocity (V) =1 m/s
ASSUMPTIONS
- Steady state
- Convection between the pipes is negligible
- The thermal resistance of the pipe walls is negligible
- The thickness of the outer pipe wall is negligible (Inside surface area = Outside surface area)
- Area of the cellar is large compared to the pipe so that cellar behaves as a blackbody enclosure at T?
- Oil has the thermal properties of unused engine oil
- The temperature of the inner pipe is constant
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant
for unused engine oil at 550 K
Density (p) = 742 kg/m3
Specific heat (c) 2998 J/(kg K)
Size of the Nucleus: A proton is projected at a stationary 
Ra aluminum target. The proton momentarily comes to a halt at a distance from the center of an aluminum nucleus, equal to twice the nuclear radius. Assume that the nucleus retains its spherical shape and that the nuclear force on the proton is negligible. The initial kinetic energy of the proton, in MeV, is closest to:
A. 8.7 MeV. B. 5.8 MeV. C. 2.9 MeV. D. 13 MeV. E. 17 MeV.