An astronaut landed on a far away planet that has a sea of water. to determine the gravitational acceleration on the planet's surface, the astronaut lowered a pressure gauge into the sea to a depth of 12.3 m. if the gauge pressure is measured to be 1.1 atm, what is the gravitational acceleration on the planet's surface? use 1000 kg/m3 as the mass density of water.

Scientists use laser range-finding to measure the distance to the moon with great accuracy. a brief laser pulse is fired at the moon, then the time interval is measured until the "echo" is seen by a telescope. a laser beam spreads out as it travels because it diffracts through a circular exit as it leaves the laser. in order for the reflected light to be bright enough to detect, the laser spot on the moon must be no more than 1.0 km in diameter. staying within this diameter is accomplished by using a special large-diameter laser. part a if λ = 540nm , what is the minimum diameter of the circular opening from which the laser beam emerges? the earth-moon distance is 384,000 km. express your answer to two significant figures and include the appropriate units.

What is hidden during a lunar eclipse? isn't the moon hidden?

True or false: the revolution of the earth creates day and night as it rotates around the sun