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Escape Velocity

Part of the Mechanics section of Coddy's Physics journey. Lesson 92 of 97.

The escape velocity is the smallest launch speed that never comes back. The object escapes when K+U\relax K + U is zero or more:

vesc=2GMR=2gRv_{\text{esc}} = \sqrt{\frac{2GM}{R}} = \sqrt{2gR}

The object's own mass cancels. At the same distance, escape speed is 2≈1.41\sqrt{2} \approx 1.41 times the orbit speed. Earth: 11.2 km/s11.2\ \mathrm{km/s}.

A planet with a dashed circular orbit around it and an open curve leaving from the same point: at the orbit speed v the object circles, at the escape speed, about 1.41 times larger, it moves away and never returns

Same starting point: orbit speed circles, escape speed never comes back.

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Challenge

A dwarf planet has a radius of 500 000 m500\,000\ \mathrm{m} and a surface gravity of 0.25 m/s20.25\ \mathrm{m/s^2}. Find its escape velocity vesc\relax v_{esc}.

Try it yourself

Physics diagram: planet, path, ball; arrows v esc = ?

Solve for vescv_{esc}

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