While exploring a castle, Exena the Exterminator is spotted by a dragon that chases her down a hallway. Exena runs into a room and attempts to swing the heavy door shut before the dragon gets her. The door is initially perpendicular to the wall, so it must be turned through 90 degrees to close. The door is 3.00 m tall and 1.25 m wide, and it weighs 750 N. You can ignore any friction. If Exena applies a force of 220 N at the edge of the door, what is the minimum time does it take her to close the door

spectral lines lyman is one set

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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it is a negative acceleration