A cluster with a lot of Type O and B stars, but no bright K or M stars, is very
A) faint.
B) poor in heavy elements.
C) young.
D) old.
E) densely packed.
C
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A motorist travels for 3.0 h at 80 km/h and 4.0 h at 60 km/h. What is her average speed for the trip?
A) 74 km/h B) 140 km/h C) 70 km/h D) 73 km/h E) 69 km/h
Photoelectric Effect: A beam of light with a frequency range from 3.01 × 1014 Hz to 6.10 × 1014 Hz is incident on a metal surface. If the work function of the metal surface is 2.20 eV, what is the maximum kinetic energy of photoelectrons ejected from this surface? (h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J)
A. 0.33 eV B. 0.21 eV C. 0.42 eV D. 0.16 eV E. 0.48 eV
Bumpers on cars are not of much use in a collision. To see why, calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm
when the car had an initial speed of 2.0 m/s (about 4.5 mph). (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.) A) 3.2 × 104 N B) 1.6 × 104 N C) 5.4 × 104 N D) 1.8 × 104 N E) 6.5 × 105 N
A 1.50-H inductor is connected in series with a 200-? resistor through an ideal 15.0-V dc power supply and an open switch. How much energy is contained in the inductor 20.0 ms after closing the switch?
A) 5.48 mJ B) 0.910 mJ C) 7.31 mJ D) 3.65 mJ E) 1.83 mJ