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
Correct answer
Explanation
The correct answer is C, one-sixth. 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. A body of sixty kilograms therefore still has a mass of sixty kilograms on the moon but weighs only about a sixth of what it weighs on the earth, which is why astronauts can take long bounding steps there.
Options A and B, one-half and one-fourth, are invented fractions with no basis in the moon's mass and radius. Option D, the same, would be true of the mass of the body but never of its weight, and this is exactly the confusion the question is designed to catch. Remember the one-line rule: mass does not change with place, weight does, and on the moon the change is a factor of about one-sixth.
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 →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
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Escape velocity is the minimum speed a body must be given so that it leaves the gravitational pull of the planet and never returns.
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.
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