A type-II supernova
a. occurs when a white dwarf's mass exceeds the Chandrasekhar limit.
b. is the result of helium flash.
c. is characterized by a spectrum that shows hydrogen lines.
d. occurs when the iron core of a massive star collapses.
e. c and d
E
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A swimmer swims 20 laps in a north-south facing pool in 7.00 minutes. Her first lap is toward the north. Her displacement and average velocity are
a. 0; 0. b. 0; 2.38 m/s, south. c. 0; 2.38 m/s, north. d. 1 000 m, south; 2.38 m/s, south. e. 1 000 m, north; 2.38 m/s, north.
If you push directly on the handle of a closed door and it does not swing open, then
A. the net torque on the door must be zero. B. the lever arm must be very small. C. its rotational inertia must be much larger than your torque. D. the angular momentum of the door is larger than your force.
A fire hose is turned on the door of a burning building in order to knock the door down. This requires a force of 1000 N
If the hose delivers 40 kg of water per second, what is the minimum velocity of the stream needed to knock down the door, assuming the water doesn't bounce back? A) 15 m/s B) 20 m/s C) 25 m/s D) 30 m/s
A mass of 0.40 kg, hanging from a spring with a spring constant of 160 N/m, is set into an up-and-down simple harmonic motion. What is the speed of the mass when moving through a point at 0.05 m displacement? The starting displacement of the mass is 0.10 m from its equilibrium position
a. zero c. 1.7 m/s b. 1.4 m/s d. 1.2 m/s