Which of the following objects is obeying Newton's laws of motion?
A. a satellite orbiting Earth
B. a runner racing around a track
C. a skydiver falling under the force of gravity
D. a sleeping cat
E. All of these choices are correct.
Answer: E
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Jet-shaped regions of radio and optical emission have been observed in
a. quasars. b. radio galaxies. c. the 3-Kelvin radiation. d. quasars and radio galaxies.
Assume that the water is originally at the freezing temperature Tf, that the cooling medium inside the tube surface is just below the freezing temperature at a uniform temperature Ts, and that ho is the total heat transfer coefficient between the cooling medium and the pipe-ice interface. Also show the thermal circuit.
Show that the dimensionless equation for ice formation at the outside of a tube of radius ro is
where
GIVEN
? Water freezing on the outside of a tube
? Tube radius = ro
? Cooling medium temperature = T ? (uniform)
? Heat transfer coefficient between the cooling medium and the pipe-ice interface = ho
FIND
? Draw the thermal circuit and show that the dimensionless equation for ice formation is as shown
above
ASSUMPTIONS
? Steady state
? The thermal capacitance of the ice layer is negligible
? T? is constant
? The water is at the freezing temperature, Tf
? The properties of the ice are uniform
SKETCH
Observer A sees a pendulum oscillating back and forth in a relativistic train and measures its period to be TA. Observer B moves together with the train and measures the period of the pendulum to be TB. These two results will be such that
A) TA > TB. B) TA = TB. C) TA < TB. D) TA could be greater or smaller than TB depending on the direction of the motion.
Fifteen microseconds is
a. 0.0000015 s. b. 0.000015 s. c. 0.00015 s. d. 0.015 s. e. 15000000 s.