Why can't a star's distance be determined solely from its apparent brightness in the sky? (a) stars move too fast (b) stars burn out before we can determine their distance (c) stars have different energy outputs (d) there's no way to measure the light from a star (e) earth's atmosphere blocks all starlight

What is the difference between electrically neutral objects and electrically charged objects

In a wind tunnel the speed changes as the cross sectional area of the tunnel changes. if the speed in a 6' x 6' square test section is 100 mph, what was the speed upstream of the test section where the tunnel measured 20' x 20'? use conservation of mass and assume incompressible flow. conservation of mass requires that as the flow moves through a path or a duct the product of the density, velocity and cross sectional area must remain constant; i. e., that ova-constant. a model is being tested in a wind tunnel at a speed of 100 mph if the flow in the test section is at sea level standard conditions, what is the pressure at the model's stagnation point? (a) the tunnel speed is being measured by a pitot-static tube connected to a u- tube manometer. what is the reading on that manometer in inches of water? (b) at one point on the model a pressure of 2058 psf is measured. what is the local airspeed at that point?

Athermometer is removed from a room where the temperature is 70° f and is taken outside, where the air temperature is 10° f. after one-half minute the thermometer reads 60° f. what is the reading of the thermometer at t = 1 min? (round your answer to two decimal places.) ° f how long will it take for the thermometer to reach 30° f? (round your answer to two decimal places.)