Question
A hollow spher is made of a lead of radius R such that its surface touches the outside surface of the lead sphere and passes through its centre. The mass of the lead sphere before hollowing was M. What is the force of attraction that this sphere would exert on a particle of mass m which lies at a distance from the centre of the lead sphere on the straight line joining the centres of the sphere and the hollow (as shown in fig.)?

None of these



medium
Solution
As the point mass m is outside the lead sphere we can assume its mass to be concentrated at the centre. To calculate the force of attraction on the point mass m we should calculate the force due to the solid sphere and subtract from this the force which the mass of the hollowed sphere would have exerted on m, i.e.,
SIMILAR QUESTIONS
A spacecraft is launched in a circular orbit near the earth. How much more velocity will be given to the spacecraft so that it will go beyond the attraction force of the earth. (Radius of the earth = 6400 km, g = 9.8 m/s^{2}).
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With what velocity must a body be thrown upward from the surface of the earth so that it reaches a height of 10 R_{e}? Earth’s mass and G = 6.67 × 10^{ –11} Nm^{2}kg^{–2}.
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The escape velocity of a body from earth is 11.2 km s^{–1}. If the radius of a planet be half the radius of the earth and its mass be onefourth that of earth, then what will be the escape velocity from the planet?
A body is at a height equal to the radius of the earth from the surface of the earth. With what velocity be it thrown so that it goes out of the gravitational field of the earth? Given:
N m^{2} kg^{–2}.
A particle falls on the surface of the earth from infinity. If the initial velocity of the particle is zero and friction due to air is negligible, find the velocity of the particle when it reaches the surface of the earth. Also find its kinetic energy. (Radius of earth is 6400 km and g is 9.8 m/s^{2}.)
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