What is escape velocity?
Escape velocity is the speed needed to break free of the gravitational pull of a large mass. “on the Sun, the Sun’s gravity: 617.5 km/s on Mercury, Mercury’s gravity: 4.4 km/s at Mercury, the Sun’s gravity: 67.7 km/s on Venus, Venus’ gravity: 10.4 km/s at Venus, the Sun’s gravity: 49.5 km/s on Earth, the Earth’s gravity: 11.2 km/s at the Earth/Moon, the Sun’s gravity: 42.1 km/s on the Moon, the Moon’s gravity: 2.4 km/s at the Moon, the Earth’s gravity: 1.4 km/s on Mars, Mars’ gravity: 5.0 km/s at Mars, the Sun’s gravity: 34.1 km/s on Jupiter, Jupiter’s gravity: 59.5 km/s at Jupiter, the Sun’s gravity: 18.5 km/s on Saturn, Saturn’s gravity: 35.5 km/s at Saturn, the Sun’s gravity: 13.6 km/s on Uranus, Uranus’ gravity: 21.3 km/s at Uranus, the Sun’s gravity: 9.6 km/s on Neptune, Neptune’s gravity: 23.5 km/s at Neptune ” http://en.wikipedia.
Escape velocity is the speed a moving object must have in order to escape from the gravitational pull exerted by another object. For example, the escape velocity from Earth’s surface is equal to about 6.8 miles per second (11 km/s). Anything that wants to escape Earth’s gravitational pull must go at least 6.8 miles per second (11 km/s), no matter what the thing is – a rocket ship or a baseball. The escape velocity of an object depends on how compact it is; that is, on the ratio of its mass to radius. A black hole is an object so compact that, within a certain distance of it, even the speed of light is not fast enough to escape.
Escape velocity is the velocity at which a body must travel before it breaks free of the gravitational pull of a celestial body. It varies widely based on the body’s mass. The Earth’s escape velocity is 11.186 km/s (25,022 mph or about Mach 37), which can only reached by powerful booster rockets. By comparison, the Space Shuttle’s top speed is about 7.6 km/sec, enough to reach Low Earth Orbit but not escape the Earth’s gravitational pull entirely. The escape velocity on Mars’ moon Phobos is about 11 m/s, or 25 mph. The body’s mean diameter is 11 km (6.8 mi). Its smaller cousin, Demos, with a mean diameter of 6 km (3.7 mi), has an escape velocity of only 6.9 m/s (15 mph), meaning that you could probably jump right off it if you tried hard enough. The gravitational force decreases with the square of the distance, meaning that if a certain distance away from the body the gravity is only half that on the surface, at twice that distance the gravity will be four times less, eight times less,
Escape velocity is the speed that an object needs to be traveling to break free of a planet or moon’s gravity well and enter orbit. For example, a spacecraft leaving the surface of Earth needs to be going 7 miles per second, or nearly 25,000 miles per hour to enter orbit. A Delta II rocket blasting off. A large amount of energy is needed to achieve escape velocity. Photo from Jet Propulsion Laboratory’s Planetary Missions & Instruments image gallery http://www-b.jpl.nasa.gov/pictures/browse/pmi.html Since escape velocity depends on the mass of the planet or moon that a spacecraft is blasting off of, a spacecraft leaving the moon’s surface could go slower than one blasting off of the Earth, because the moon has less gravity than the Earth. On the other hand, the escape velocity for Jupiter would be many times that of Earth’s because Jupiter is so huge and has so much gravity.
You remember the fantasy: If you could jump high enough, you could leave Earth and bound up to the moon. To pull off that colossal kangaroo act, you’d have to reach escape velocity — the minimum velocity needed to permanently escape the gravity of a planet or star. Escape velocity is even simpler to calculate than orbital velocity. In general, all you need to know are the gravitational constant (“G”), the mass of the planet or star, and the distance of the spaceship from the center of mass of the planet or star. (Need information on units?) We had an encyclopedia do the math for us, and learned that escape velocity at Earth’s surface is 11,200 meters per second. Just as with orbital velocity, the further from Earth, the lower the escape velocity.
