Time Dilation: An astronaut on a spaceship moving at 0.927c says that the trip between two stationary stars took 4.26 y. How long does this journey appear to take to someone in the rest frame of the two stars?
A. 11.4 y
B. 1.60 y
C. 2.30 y
D. 12.6 y
Answer: A
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Derive an equation for the net rate of radiant heat transfer from surface 1 in the system shown in the accompanying sketch. Assume that each surface is at a uniform temperature and that the geometrical shape factor F1–2 is 0.1.
IVEN
• The system shown above
FIND
• An expression for the net rate of radiant heat transfer from surface 1 (q1) ASSUMPTIONS
• Steady state
• A1 and A2 are gray, A0 is black
• Each surface is at a uniform temperature
• The shape factor F12 = 0.1
PROPERTIES AND CONSTANTS
he Stephan-Boltzmann constant (?) = 5.67× 10–8 W/(m2 K4)
An object that acts as a blackbody emits photons because ____
a. thermal energy excites electrons to the ground state b. electrons in the atoms of the object jump to lower energy levels c. electrons in the atoms of the object jump to higher energy levels d. atoms in the object collide, changing the motion of charged particles e. atoms in the object have absorbed photons from an external source
A rotating flywheel can be used as a method to store energy. If it has 2.0 × 10^6 J of kinetic energy when rotating at 400 rad/s, and if a frictional torque of 4.0 Nm acts on the system, in what interval of time would the flywheel come to rest?
a. 3.5 min c. 14 min b. 42 min d. 21 min
Why is spectral intensity not diminished by the distance from the source of radiation?
What will be an ideal response?