When did scientists first detect gravitational waves from mergers of compact objects (pairs of neutron stars or black holes)?
A) 2015
B) 1543
C) 1990
D) Gravitational waves have not yet been detected, though scientists hope to detect them soon.
A) 2015
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A string is stretched with a tension of 120 N. The string has a mass of 10.0 grams and has a length of 2.50 meters. The velocity of wave propagation along the string is
A. 125 m/s. B. 142 m/s. C. 173 m/s. D. 185 m/s. E. 217 m/s.
Like our own moon, many Jovian moons exhibit what is called synchronous rotation. This means that they rotate at the same rate
A) that their host planet rotates B) as all other moons around the host planet C) that the host planet orbits about the Sun D) that they orbit their host planet
The heat conduction equation in cylindrical coordinates is
(a) Simplify this equation by eliminating terms equal to zero for the case of steady-state heat flow
without sources or sinks around a right-angle corner such as the one in the accompanying
sketch. It may be assumed that the corner extends to infinity in the direction perpendicular to
the page. (b) Solve the resulting equation for the temperature distribution by substituting the
boundary condition. (c) Determine the rate of heat flow from T1 to T2. Assume k = 1 W/(m K)
and unit depth .
GIVEN
• Steady state conditions
• Right-angle corner as shown below
• No sources or sinks
• Thermal conductivity (k) = 1 W/(m K)
FIND
(a) Simplified heat conduction equation (b) Solution for the temperature distribution (c) Rate of heat flow from T1 to T2 ASSUMPTIONS
• Corner extends to infinity perpendicular to the paper
• No heat transfer in the z direction
• Heat transfer through the insulation is negligible
SKETCH
A solid object is made of two materials, one material having density of 2 500 kg/m3 and the other having density of 6 000 kg/m3 . If the object contains equal volumes of the materials, what is its average density?
a. 3 529 kg/m3 b. 4 250 kg/m3 c. 5 250 kg/m3 d. 8 500 kg/m3 e. more information is needed