A 5-kg boulder sits on the edge of a cliff 30 m above the roadway. What is the gravitational potential energy of the boulder on the cliff ?

What is the earliest point in the universe that we can observe? why can’t we see back further than this?

Light from a sodium lamp passes through a diffraction grating that has 1000 slits per millimeter. the interference pattern is viewed on a screen 1.000 m behind the grating. the first (m = 1) two bright yellow fringes that are visible are 0.7288 m and 0.7300 m from the central maximum. what are the wavelengths of these two fringes?

What is the orbital period of a spacecraft in a low orbit near the surface of mars? the radius of mars is 3.4×106m.