For the aluminum alloy 7075-T6, shown in Figure 11.23, a stress amplitude of 250 MPa is applied for 106 cycles to a group of 100 specimens. How many of these specimens should fail in this test?
What will be an ideal response?
In Figure 11.21 draw a vertical line from 106 cycles and a horizontal line at 250 MPa the two lines intersect very close to the 50% probability of failure line. Thus approximately 50 of the specimens should fail.
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Which of the following best describes why the Sun emits most of its energy in the form of visible light?
A) Nuclear fusion in the Sun's core produces visible light photons. B) The Sun's gas is on fire like flames from wood or coal, and these flames emit visible light. C) Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light. D) The visible light comes from energy level transitions as electrons in the Sun's hydrogen atoms jump between level 1 and level 2.
Why have most extrasolar planets detected with the transit method been found with orbits fairly close to their host stars?
A) They transit more frequently and are more likely to be detected in the short time we have been searching for them. B) More of the starlight is blocked by the planet when it transits the star. C) The wavelength shift of the star's spectrum is larger. D) The closer to a star, the hotter and therefore brighter the planet is. E) Planets that are close to a star are heated up and therefore larger.
Elementary Particles: The neutron is made up of which one of the following quark combinations (up, down, strange, charm, top, bottom)?
A. uud B. ddu C. udd D. ttb E. bst
Equal charges, one at rest, the other having a velocity of 104 m/s, are released in a uniform magnetic field. Which charge has the largest force exerted on it by the magnetic field?
a. The charge that is at rest. b. The charge that is moving, if its velocity is parallel to the magnetic field direction when it is released. c. The charge that is moving if its velocity makes an angle of 45o with the direction of the magnetic field when it is released. d. The charge that is moving if its velocity is perpendicular to the magnetic field direction when it is released. e. All the charges above experience equal forces when released in the same magnetic field.