A stunt pilot weighing 0.70 kN performs a vertical circular dive of radius 0.80 km. At the bottom of the dive, the pilot has a speed of 0.20 km/s which at that instant is not changing. What force does the plane exert on the pilot?
A. 3.6 kN up
B. 4.3 kN up
C. 2.9 kN down
D. 2.9 kN up
E. 5.8 kN down
Answer: 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.
A real gas undergoes a process that can be represented as a curve on a p-V diagram. The work done by the gas during this process is:
A. pV B. p(V2 ? V1) C. (p2 ? p1)V D. $ p dV E. V dp
Thermal energy will flow in a direction from cold to hot
A) only with external effort. B) near absolute zero. C) never. D) always.
A Frisbee is thrown horizontally by a student and travels in a straight line. Viewed from above, the Frisbee is seen to be in clockwise rotation. From the point of view of the student, in which direction is the angular momentum of the Frisbee while in flight?
a. The Frisbee has no angular momentum since it is moving along a straight line away from the student. b. The direction of the angular momentum is along the line away from the student. c. The direction of the angular momentum is toward the right since this was a right-handed throw. d. The direction of the angular momentum is downward, perpendicular to the path of the Frisbee.