What two observable properties of a Cepheid variable are directly related to one another?
A) the period between its peaks of brightness and its luminosity
B) the period between its peaks of brightness and its distance
C) its luminosity and its mass
D) its mass and its distance
A) the period between its peaks of brightness and its luminosity
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A major source of chlorine gas, Cl2, is from the electrolysis of brine, which is concentrated salt water, Which of the following is the balanced chemical reaction for this electrolysis reaction?
A. 2 NaCl (aq) + H2O ? 2 NaH (aq) + Cl2O (aq)
B. 2 NaCl (aq) + 2 H2O ? 2 Na (s) + O2 (g) + 2 H2 (g) + Cl2 (g)
C. 2 NaCl (aq) + H2O ? Na2O (aq) + 2 HCl (aq)
D. 2 NaCl (aq) + 2 H2O ? 2 NaOH (aq) + Cl2 (g) + 2 H2 (g)
The temperature of melting ice is
A) 0°C. B) 32°F. C) both of these
A CD with a diameter of 12.0 cm starts from rest and with a constant angular acceleration of 1.00 
acquires an angular velocity of 5.00 rad/sec. The CD continues rotating at 5.00 rad/sec for 15.0 seconds and then slows to a stop in 12.0 second with a constant angular deceleration. What is the total acceleration of a point 4.00 cm from the center at the time 2.00 seconds from the start?
A. 0.450 
B. 0.314
C. 0.215
D. 0.165
E. 0.100
What is the impedance of an AC series circuit that is constructed of a 10.0-? resistor along with 24.0-? inductive reactance and 7.0-? capacitive reactance?
a. 19.7 ? b. 11.2 ? c. 41.0 ? d. 27.7 ?