| 1. |
 Equal masses m hang from strings of different lengths on a balance at the surface of the Earth as shown in the figure. The strings have negligible mass and differ in length by h. Find the error in weighing due to the difference in heights of the masses from the surface. Given that the density of the Earth is  .
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| 2. |
A binary system of stars consists of two stars moving around the center of inertia of the system due to gravitation. What is the distance between the stars if the mass of the whole system is m and the time period of revolution is T? |
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| 3. |
A length of wire of mass M is bent into an arc of a circle of radius R, subtending an angle of ø at the center. A particle of mass m is placed at the center. What force does the wire apply on the particle? |
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