Chapter 7: Problem 25
The period of revolution of planet \(A\) around the sun is 8 times that of \(B\). The distance of \(A\) from the sun is how many times greater than that of \(B\) from the sun? (A) 2 (B) 3 (C) 4 (D) 5
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Chapter 7: Problem 25
The period of revolution of planet \(A\) around the sun is 8 times that of \(B\). The distance of \(A\) from the sun is how many times greater than that of \(B\) from the sun? (A) 2 (B) 3 (C) 4 (D) 5
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Both the earth and the moon are subject to the gravitational force of the sun. As observed from the sun, the orbit of the moon (A) will be elliptical. (B) will not be strictly elliptical because the total gravitational force on it is not central. (C) is not elliptical but will necessarily be a closed curve. (D) deviates considerably from being elliptical due to influence of planets other than the earth.
A sphere of density \(\rho\) and radius \(a\) has a concentric cavity of radius
\(b\) as shown in the Fig. \(7.13\).
Gravitational potential energy as a function of \(r\), where \(r\) is the distance
from the centre of the sphere. When \(0
A solid sphere of uniform density and radius 4 units is located with its centre at the origin \(O\) of co-ordinates. Two spheres of equal radii 1 units, with their centres at \(A(-2,0,0)\) and \(B(2,0,0)\) respectively, are taken out of the solid leaving behind spherical cavities as shown in Fig. 7.12. Then (A) the gravitational field due to this object at the origin is zero. (B) the gravitational field at the point \(B(2,0,0)\) is zero. (C) the gravitational potential is same at all points on the circle \(y^{2}+z^{2}=36\) (D) the gravitational potential is same at all points on the circle \(y^{2}+z^{2}=4\)
Different points in the earth are at slightly different distances from the sun and hence experience different forces due to gravitation. For a rigid body, we know that if various forces act at various points in it, the resultant motion is as if a net force acts on the CM (centre of mass) causing translation and a net torque at the CM causing rotation around an axis through the CM. For the earth-sun system (approximating the earth as a uniform density sphere). (A) The torque is zero. (B) The torque cause the earth to spin. (C) The rigid body result is not applicable since the earth is not even approximately a rigid body. (D) The torque causes the earth to move around the sun.
Three planets of same density have radii \(R_{1}, R_{2}\) and \(R_{3}\) such that \(R_{1}=2 R_{2}=3 R_{3}\). The gravitational field at their respective surfaces are \(g_{1}, g_{2}\) and \(g_{3}\) and escape velocities from their surfaces are \(v_{1}, v_{2}\) and \(v_{3}\) respectively, then (A) \(g_{1} / g_{2}=2\) (B) \(g_{1} / g_{3}=3\) (C) \(v_{1} / v_{2}=1 / 4\) (D) \(v_{1} / v_{3}=3\)
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