Four particles, each with mass m, are arranged symmetrically about the origin on the x axis. a fifth particle, with mass m, is on the y axis. the direction of the gravitational force on m is:

Explanation:

Let four particles are placed on X axis symmetrically about the origin and M is placed on y axis.

According to the diagram, the x component of forces balances each other and the net force acting on the particle of mass m is acting in the direction of negative Y axis.

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if the thermos has a vacuum innner, then heat through conv currents and conduction are reduced = vacuum flask