Of the possible statements that parallel rays are brought to a focus by a 1) concave mirror, 2) convex mirror, 3) converging lens, 4) diverging lens, the correct answer is
a. 1 and 2.
b. 3 and 4.
c. 1 and 3.
d. 2 and 3.
e. 2 and 4.
c
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Two point charges of +1.0 ?C and -2.0 ?C are located 0.50 m apart. What is the minimum amount of work needed to move the charges apart to double the distance between them? (k = 1/4??0 = 8.99 × 109 N ? m2/C2)
A) -36 mJ B) +18 mJ C) 0 mJ D) +36 mJ E) -18 mJ
A light-emitting diode has a power output of 0.3 W. If 590 nm is the average wavelength of the source, about how many photons are emitted per second? (h = 6.63 × 10^?34 J?s, c = 3.00 × 10^8 m/s, and 1 nm = 10?9 m)
a. 1021 b. 1025 c. 1018 d. 1029
A child is standing at the rim of a freely rotating disk holding a rock. The disk rotates without friction. The rock is dropped at the instant shown. Which of the following statements is true about the process of dropping the rock?
A single force acts on an object and the torque caused by the force is nonzero about some point. Is there any other point about which the torque is zero?
1.Yes, under any circumstance there is such a point. 2.No. 3.Yes, but only if the force is centripetal. 4.It is impossible to determine.