Suppose we were in a spaceship in free fall, where objects are weightless, and wanted to know a small solid object’s mass. We could not simply balance that object against another of known weight, as we would on Earth. The unknown mass could be determined, however, by placing the object on a spring scale and swinging the scale in a circle at the end of a string. The scale would measure the tension in the [gl]string[/gl], which would depend on both the speed of revolution and the mass of the object. The tension would be greater, the greater the mass or the greater the speed of revolution. From the measured tension and speed of whirling, we could determine the object’s mass.

Astronomers use an analogous procedure to “weigh” double-star systems. The speed with which the two stars in a double-star system circle one another depends on the gravitational force between them, which holds the system together. This attractive force, analogous to the tension in the string, is proportional to the stars’ combined mass, according to Newton’s law of gravitation. By observing the time required for the stars to circle each other (the period) and measuring the distance between them, we can deduce the restraining force, and hence the masses.

Q1 :- It can be inferred from the passage that the two procedures described in the passage have which of the following in common?
A They have been applied in practice.
B They rely on the use of a device that measures tension.
C Their purpose is to determine an unknown mass.
D They can only be applied to small solid objects.
E They involve attraction between objects of similar mass.




Q2 :- According to the passage, the tension in the string mentioned in highlight text is analogous to which of the following aspects of a double-star system?
A The speed with which one star orbits the other
B The gravitational attraction between the stars
C The amount of time it takes for the stars to circle one another
D The distance between the two stars
E The combined mass of the two stars




Q3 :- Which of the following best describes the relationship between the first and the second paragraph of the passage?
A The first paragraph provides an illustration useful for understanding a procedure described in the second paragraph.
B The first paragraph describes a hypothetical situation whose plausibility is tested in the second paragraph.
C The first paragraph evaluates the usefulness of a procedure whose application is described further in the second paragraph.
D The second paragraph provides evidence to support a claim made in the first paragraph.
E The second paragraph analyzes the practical implications of a methodology proposed in the first paragraph.



Q4 :- The author of the passage mentions observations regarding the period of a double-star system as being useful for determining
A the distance between the two stars in the system
B the time it takes for each star to rotate on its axis
C the size of the orbit the system’s two stars occupy
D the degree of gravitational attraction between the system’s stars
E the speed at which the star system moves through space