A certain siren radiates sound uniformly in all directions. At a distance of 17 m from the siren, the intensity level is 49 db. How many watts of power does this siren put out? The threshold of human hearing is 1.0 × 10-12 W/m2
What will be an ideal response?
2.9 × 10-4 W
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Newton's law of gravitational force is expressed as follows:
a. An object with no force on it moves in a straight line with constant velocity. b. An object with a force on it is accelerated in the direction of the force an amount inversely proportional to its mass and directly proportional to the size of the force. c. For every action there is an equal and opposite reaction. d. The force between two objects is directly proportional to the product of their masses and inversely proportional to the distance between them squared.
A proton and a deuteron are moving with equal velocities perpendicular to a uniform magnetic field. A deuteron has the same charge as the proton but has twice its mass. The ratio of the acceleration of the proton to that of the deuteron is:
a. 0.5. b. 1. c. 2. d. There is no acceleration in this case.
A cylindrical metal wire at room temperature is carrying electric current between its ends. One end is at potential VA = 50 V, and the other end is at potential VB = 0 V. Rank the following actions in terms of the change that each one separately would produce in the current from the greatest increase to the greatest decrease. In your ranking, note any cases of equality
(a) Make VA = 150 V with VB = 0 V. (b) Adjust VA to triple the power with which the wire converts electrically transmitted energy into internal energy. (c) Double the radius of the wire. (d) Double the length of the wire. (e) Double the Celsius temperature of the wire.
1.b > c > a > e > d 2.d > a > c > b > e 3.c > a > b> e > d 4.a > c > d > e > b 5.None of these.Suppose both of the new charges from questions 41 and 41 are in their respective positions simultaneously. The forces on each of them are
a. still zero b. in the same directions as they were when each was alone c. both in new directions d. the same as before for the positive charge but different for the negative charge