A student has made the statement that the electric flux through one half of a Gaussian surface is always equal and opposite to the flux through the other half of the Gaussian surface. This is
a. never true. b. never false. c. true whenever enclosed charge is symmetrically located at a center point, or on a center line or centrally placed plane. d. true whenever no charge is enclosed within the Gaussian surface. e. true only when no charge is enclosed within the Gaussian surface.
E
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An object is placed a distance d from a converging lens. The object is then moved to a distance 2d from the converging lens. Which of the following statements is false?
a. The image in the second case with the object at distance 2d can be the larger one. b. If both images are real, the image in the second case is smaller. c. If the image in the first case is real, the image in the second case is upright. d. The image in the first case with the object at distance d can be the larger one.
a uniaxial composite material is made into a circular rod with a 1.27 cm diameter from 70 vol % continuous carbon fibers and 30 vol % epoxy. The rod is subject to an axial force of 100,000 N. The composite material in Example Problem 12.1 is to be replaced with a less expensive composite made of 70 vol % continuous E-glass fibers and 30 vol % epoxy. The elastic moduli are 5 GPa for the epoxy resin and 72.4 GPa for the E-glass.
(a) Compare the elastic modulus, composite strain, fiber and matrix stresses, and density of this composite with the carbon epoxy composite in Example Problem 12.1. Use the density of UHM carbon, and assume the density of the epoxy is 1.2 g/cm3. (b) Can both the E-glass fiber and matrix withstand the applied force?
Which statement must be true for a rocket to travel from Earth to another planet?
A) It must attain escape velocity from Earth. B) It must carry a lot of extra fuel. C) It must have large engines. D) It must be launched from space, rather than from the ground.
Suppose that an object is moving with constant acceleration. Which of the following is an accurate statement concerning its motion?
A) In equal times its speed increases by equal amounts. B) In equal times its velocity changes by equal amounts. C) In equal times it moves equal distances.