The most common stars in the universe are red dwarf stars. Red dwarf stars use their hydrogen fuel very slowly. Our universe also contains stars classified as blue supergiants. The table below lists the color and approximate surface temperatures of four stars. Based on the information from the table above, which of the following stars has the greatest absolute brightness? The Sun

Vega

Bellatrix

Betelgeuse

Acoal-fired plant generates 600 mw of electric power. the plant uses 4.8 x 10^6 kg of coal each day, and the heat of combustion of coal is 3.3x 10^7 j/kg. the steam that drives the turbines is at a temperature of 300° c, and the exhaust water is at 37° c. (a) what is the overall efficiency of the plant for generating electric power? (b) how much thermal energy is exhausted each day? (c) what is the change in entropy of the universe for this heat engine? (d) using the same heat reservoirs, what is the maximum possible (carnot) efficiency for a heat engine?

An object that weighs 75n is pulled on a horizontal surface by a horizontal pull of 50 n to the right. the friction force on this object is 30 n to the left. what is the acceleration of the object?

Neurons are components of the nervous system of the body that transmit signals as electrical impulses travel along their length. these impulses propagate when charge suddenly rushes into and then out of a part of the neutron called an axon. measurements have shown that, during the inflow part of this cycle approximately 5.6x10^11 na per meter, each with a charge of e enter the axon. how many coulombs of charge enter a 1.10 cm length of axon during this process