A magnifying lens with a focal length of 30 cm has what magnification when the viewing eye is relaxed?
a. 7.14
b. 0.8
c. 1.3
d. 1.8
e. –0.2
b
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A uniaxial composite material is made from 75 vol %t continuous kevlar fibers and 25 vol %t epoxy. The kevlar fibers have an elastic modulus of 131×109 Pa and a tensile strength of 4.0×109 Pa. The epoxy resin has an elastic modulus of 5×109 Pa and a tensile strength of 50×106 Pa.
(a) In a uniaxial test to failure, what component will fail first, and at what strain? (b) What is the composite stress at fracture of the first component? Assume that both the kevlar fibers and the epoxy matrix are elastic up to their failures.
Velocity: The position x(t) of a particle as a function of time t is given by the equation x(t) = (3.5 m/s)t - (5.0 m/s2)t2. What is the average velocity of the particle between t = 0.30 s and t = 0.40 s?
Fill in the blank(s) with the appropriate word(s).
The SI units for k, the spring constant, are equivalent to:
a. J c. kg / s2 b. J / N d. none of the above
Which forms of light are lower in energy and frequency than the light that our eyes can see?
A) infrared and radio B) ultraviolet and x-rays C) visible light D) infrared and ultraviolet