The escape velocity from the surface of the earth is approximately
- A.7.9 kilometres per second
- B.9.8 kilometres per second
- C.11.2 kilometres per second
- D.24 kilometres per second
Correct answer
Explanation
The correct answer is C, 11.2 kilometres per second. Escape velocity is the minimum speed a body must be given so that it leaves the gravitational pull of the planet and never returns. It depends only on the mass and radius of the planet and not on the mass of the body projected or on the direction of projection, and for the earth it works out at about 11.2 kilometres per second.
Option A, about 7.9 kilometres per second, is the orbital velocity for a satellite close to the earth's surface, and it is smaller than the escape velocity by a factor of the square root of two. Option B, 9.8, is the numerical value of the acceleration due to gravity in metres per second squared and has nothing to do with escape velocity except as a familiar number. Option D is far too large for the earth. The moon's escape velocity is only about 2.4 kilometres per second, which is why it cannot retain an atmosphere.
Read the full article: Gravitation and Pressure: Laws, Formulas and Facts
Practice Questions
View allWhat is the SI unit of pressure?
- A.Newton
- B.Pascal
- C.Joule
- D.Watt
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Pressure is thrust per unit area, so its unit is one newton per square metre, and this unit is named the pascal after Blaise Pascal.
Read the full explanation →The value of acceleration due to gravity on the earth is maximum at which of the following?
- A.The equator
- B.The poles
- C.The centre of the earth
- D.The top of Mount Everest
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The earth is flattened at the poles, so the distance from the centre is least there, and since g varies inversely as the square of that distance, g is largest at the poles.
Read the full explanation →Hydraulic brakes used in automobiles work on which principle?
- A.Archimedes' principle
- B.Pascal's law
- C.Bernoulli's principle
- D.Newton's law of gravitation
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Pascal's law states that pressure applied to an enclosed fluid is transmitted undiminished in every direction to all parts of the fluid and to the walls of the container.
Read the full explanation →The upward force experienced by a body immersed in a fluid is equal to the weight of the fluid displaced by it. This statement is known as
- A.Pascal's law
- B.Archimedes' principle
- C.Hooke's law
- D.Boyle's law
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It states that a body immersed wholly or partly in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced, so the apparent loss in weight of the body equals the weight of the displaced fluid.
Read the full explanation →The weight of a body on the surface of the moon is about how much of its weight on the surface of the earth?
- A.One-half
- B.One-fourth
- C.One-sixth
- D.The same
Show answer
Weight equals mass times the acceleration due to gravity, and the acceleration due to gravity on the moon is about one-sixth of its value on the earth because the moon has a much smaller mass and a smaller radius.
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