Positive work can be done
a. by friction on the tires when a car is accelerating without skidding.
b. by a spring when it launches a clown in the air.
c. by a hand throwing a ball.
d. by all of the above. e. only by (b) and (c) above.
E
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Changing the f-number of a camera by two stops by going from f/16 to f/8 will change the intensity of the light hitting the film by a factor of:
a. 4. c. 1/4. b. 1/2. d. 2.
Each of two long straight parallel wires separated by a distance of 16 cm carries a current of 20 A in the same direction. What is the magnitude of the resulting magnetic field at a point that is 10 cm from each wire?
a. 57 mT b. 80 mT c. 64 mT d. 48 mT e. 40 mT
Series/Parallel Circuits: Three resistors with resistances of 2.0 ?, 6.0 ?, and 12 ? are connected across an ideal dc voltage source V as shown in the figure. If the total current through the circuit is I = 2.0 A, what is the applied voltage V?
A. 6.0 V B. 3.0 V C. 2.0 V D. 2.7 V E. 1.5 V
An emf of 0.52 V is induced in a 0.71-H inductor. What is the rate of change of current through the inductor?
a. 0.73 A/s b. 1.4 A/s c. 0.37 A/s d. 1.23 A/s e. 0.71 A/s