An astronaut, whose mission is to go where no one has gone before, lands on a spherical planet in a distant galaxy.
as she stands on the surface of the planet, she releases a small rock from rest and finds that it takes the rock 0.420 s to fall 1.90 m.
a) if the radius of the planet is 7.40×107 m,
b) what is the mass of the planet?

Explanation:

As we know that the that the Astronaut dropped a stone on the surface of the planet takes 0.420 s to fall a distance of d = 1.90 m

so we will have

now we know that the acceleration due to gravity is given as

so we will have

firearm identification is the process of analyzing the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. marks on the bullets and cartridges may be common to every firearm of that type. these are called class characteristics.

3. dark matter

empty space could also be a simple vacuum