A boat, whose speed in still water is 8.0 m/s, crosses a river with a current of 6.0 m/s. If the boat heads perpendicular to the current, what is the speed of the boat relative to an observer standing on the shore as it crosses the river?
A) 5.3 m/s B) 10.0 m/s C) 8.0 m/s D) 6.0 m/s
B
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Commercial-purity titanium reinforced with 50 % uniaxial continuous silicon carbide fibers has been proposed for use as a fan-blade material in gas turbines, because the high elastic modulus will reduce blade deflection. The yield strength of the commercial-purity titanium is 414 MPa, and the elastic modulus is 170 GPa. Assume that the titanium is perfectly plastic after yield, thus the yield and tensile strength are equal. The strain at fracture of the titanium is 25 %. The tensile strength of the silicon carbide fibers is 3.9 GPa, and the elastic modulus is 400 GPa.
(a) Calculate the strain where the first change in elastic modulus occurs in this composite material for a uniaxial tensile stress parallel to the fibers. (b) Calculate the composite stress where the change in elastic modulus occurs. (c) Calculate the elastic modulus at low strain, and if the titanium yields before the fibers fail, calculate the elastic modulus after the titanium yields. (d) Calculate the fracture strength of the composite.
On a winter day the temperature is 5 degrees Celsius and the humidity is 0.003 kilograms per cubic meter. (a) What is the relative humidity? (b) The air is brought into a building and heated to 20 degrees Celsius without changing the humidity. What is the relative humidity inside the building?
A _____ is an electronic device consisting of a large array of light-sensitive elements used to record very faint images
A) photometer B) charge-coupled device C) spectrograph D) photographic plate
A heat engine having the maximum possible efficiency has an efficiency of 25% when operating between two heat reservoirs. If the temperature of the cold reservoir is 300 K, what is the temperature of the hot reservoir?
A) 375 K B) 450 K C) 400 K D) 350 K E) 500 K