Class 11

Science

Physics

Gravitation

If g is the acceleration due to gravity on the earth's surface, the gain in the potential energy of an object of mass m raised from the surface of the earth to a height equal to the radius R of the earth, is

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Suppose the earth increases its speed of rotation . At what new time period will the weightof a body on the equator becomes zero? Take $g=10s_{2}m $ and radius of the earth $R=6400km$.

A black hole is an object whose gravitational field is so strong that even light cannot escape from it. To what approximate radius would earth (mass $=5.98×10_{24}kg$) have to be compresed to be a black hole?

A satellite of mass $m$ is orbiting the earth (of radius $R$) at a height $h$ from its surface. The total energy of the satellite in terms of $g_{0}$, the value of acceleration due to gravity at the earth's surface,

Two stars each of one solar mass $(=2×10_{30}kg)$ are approaching each other for a head on collision. When they are a distance $10_{9}km$, their speeds are negligible. What is the speed with which they collide ? The radius of each star is $10_{4}km$. Assume the stars to remain undistorted until they collide. (Use the known value of G).

The earth is assumed to be a sphere of raduis $R$. A plateform is arranged at a height $R$ from the surface of the $fv_{e}$, where $v_{e}$ is its escape velocity form the surface of the earth. The value of $f$ is

Buoyant force on an object immersed in a liquid acts in upward direction.

Why does a black of wood held under water rise to the surface when released?