A concave spherical mirror with a radius of 20 cm creates a real image 30 cm from the mirror. How far is the object from the mirror?
A) 50 cm
B) 20 cm
C) 15 cm
D) 7.5 cm
E) 5.0 cm
Answer: C
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Water flowing in a pipe is similar to electric current flowing in a circuit. Which concept in the water flow system is analogous to the charge in an electric circuit?
a) Pump
b) water
c) valve
d) pressure
Suppose that Al the physicist observes a single radioactive nucleus. The length of time until that particular nucleus decays is
A) unpredictable because of the practical difficulties of obtaining all the information needed to make the prediction. B) unpredictable because of fundamental uncertainties arising from quantum physics C) predictable from the known half-life of the nucleus. D) unpredictable because of fundamental uncertainties arising from Newtonian physics. E) predictable, provided Al knows the precise nuclear state of this nucleus.
LR Circuits: The figure shows a circuit. The ideal battery has a constant terminal voltage of ? = 27 V, the inductance is L = 0.40 H, and the resistances are R1 = 12 ? and R2 = 9.0 ?. Initially the switch S is open with no currents flowing. Then the switch is suddenly closed.(a) What is the current in the resistor R1 the instant after the switch is closed?(b) After leaving the switch has been closed for a very long time, it is opened again. Just after it is opened, what is the current in R1?
Fill in the blank(s) with the appropriate word(s).
The most accurate way of finding the distance to some very far away stars might be by observing
A. the rate of variation in their luminosity. B. their motion relative to nearby stars. C. their orbiting planets. D. the variation in their position in the night sky on successive nights.