[Physics] Physics Question

Suppose N electron can be placed in either of two configurations. In configuration 1, they are all placed on the circumference of a narrow ring of radius R and uniformly distributed so that the difference between adjacent electron is the same everywhere. In configuration 2, N-1 electrons are uniformly distributed on the ring and one electron is placed in the center of the ring. What is the smallest value of N for which the second configuration is less energetic than the first?

A 55kg person is standing at the left end of a 240kg cart moving to the left at 7.6 m/s. She runs to the right end and continues horizontally off the cart. What should be her speed relative to the cart in order to leave the cart with no horizontal velocity component relative to the ground?

The volume of a 25g wooden block is V cm^3 . The wooden block floats just below the water surface when a 5g mass is attached to the bottom as shown in the diagram below.
What is the volume of the wooden block, V?


A 20 cm^3 B 22 cm^3 C 25 cm^3 D 28cm3 E 30cm^3

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