An astronaut weighs 104 newtons on the moon, where the strength of gravity is 1.6N/kg. What is her mass?

in this image, you can see solar radiation going through ocean water.

no image, but probably absorption

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.