Find the speed needed to escape a planet's gravity.
Escape velocity is the minimum speed an object needs to break free from a body's gravity without further propulsion. It comes from setting kinetic energy equal to gravitational potential energy, giving v = √(2GM/r), where G is the gravitational constant, M the mass of the body, and r the distance from its centre.
Enter the mass of the planet or star and its radius. The default values are for Earth, giving an escape velocity of about 11.2 km/s. Notice that escape velocity is independent of the escaping object's mass, so a rocket and a pebble need the same speed to leave a planet behind.
No. The escaping mass cancels out, so all objects need the same escape speed from a given body, regardless of how heavy they are.
About 11.2 km/s, or roughly 40 000 km/h, ignoring air resistance and the Earth's rotation.