[H3O+] is just the same with [H+]. There are quite a few
relationships between [H+] and [OH−]
ions. And because there is a large range of number between 10 to 10-15
M, the pH is used. pH = -log[H+] and pOH = -log[OH−]. In aqueous solutions, [H+
][OH- ] = 10-14.
Answer:

Explanation:
Orbital velocity is the speed that a body that orbits around another body must have, for its orbit to be stable. For orbits with small eccentricity and when one of the masses is almost negligible compared to the other mass, like in this case, the orbital speed is given by:

Where M is the greater mass around which this negligible body is orbiting, r is the radius of the greater mass and G is the universal gravitational constant. So:

Explanation:
A projectile (Cannon ball) is launched at an angle to the horizontal and rises up to a peak while moving horizontally. When it reaches the peak, the projectile starts to fall.