Q38 of 81 Page 225

A particle is fired vertically upward with a speed of 15 km s-1. With what speed will it move in interstellar space. Assume only earth’s gravitational field.

Let the mass of the particle be m and the initial velocity

Here, initial kinetic energy,


Initial potential energy,


Let the final velocity be . Hence, final kinetic energy is


And since the particle is drifting in space, under no influence of gravity, its final potential energy


Now, using energy conservation,








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