What type of star has an absolute brightness of −3 and a surface temperature around 20,000 °C?

The HR diagram is shown with Absolute Brightness on the y axis from negative four to six and Surface Temperature on the x axis from 40,000 to 2,500 degrees Celsius. There are several dots plotted between four and six absolute brightness and 10,000 to 2,500 degrees Celsius labeled Supergiants. There are several dots plotted between 1.5 and three absolute brightness and 7,500 to 2,500 degrees Celsius labeled Giants. There are several dots plotted between negative four and negative two absolute brightness and 30,000 to 7,500 degrees Celsius labeled Dwarfs. Down the middle, there are several dots plotted diagonally from ordered pair 40,000 and five down to 2,500 and negative three labeled Main Sequence.

Supergiant
Giant
Main sequence
Dwarf

Awind turbine is initially spinning at a constant angular speed. as the wind's strength gradually increases, the turbine experiences a constant angular acceleration 0.173 rad/s2. after making 2870 revolutions, its angular speed is 132 rad/s. (a) what is the initial angular velocity of the turbine? (b) how much time elapses while the turbine is speeding up?

Na food processing facility, a spherical container of inner radius r1 5 40 cm, outer radius r2 5 41 cm, and ther- mal conductivity k 5 1.5 w/m · k is used to store hot water and to keep it at 100°c at all times. to accomplish this, the outer surface of the container is wrapped with a 800-w electric strip heater and then insulated. the temperature of the inner surface of the container is observed to be nearly 120°c at all times. as- suming 10 percent of the heat generated in the heater is lost through the insulation, (a) express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the container, (b) obtain a relation for the variation of temperature in the container material by solving the differential equation, and (c) evaluate the outer surface tempera- ture of the container. also determine how much water at 100°c this tank can supply steadily if the cold water enters at 20°c.

Aphoton is absorbed by an electron that is in the n = 3 state of a hydrogen atom, causing the hydrogen atom to become ionized. very far away from the nucleus, the released electron has a velocity of 750,000 m/s. what was the wavelength of the absorbed photon?