Practice free Gravitation (Physics) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
Which of the following is NOT true regarding gravitational force due to a hollow spherical shell of uniform density?
The NCERT clearly states, 'Gravitational shielding is not possible.' Options 1, 2, and 3 are correct descriptions based on the provided text.
If the Earth is considered as a collection of concentric shells, and a point mass is at a point P inside the Earth (at a distance r from the center), which shells contribute to the gravitational force on P?
The NCERT states, 'For the shells of radius greater than r, the point P lies inside. Hence according to result stated in the last section, they exert no gravitational force on mass m kept at P. The shells with radius $\le r$ make up a sphere of radius r for which the point P lies on the sur face. This smaller sphere therefore exerts a force on a mass m at P as if its mass Mr is concentrated at the centre.'
If a particle of mass m is placed inside a homogeneous solid sphere of mass M and radius R at a distance r from its center ($r < R$), the magnitude of the gravitational force on the particle is given by:
For a point inside a homogeneous solid sphere, the force is due to the mass $M_r$ of the sphere of radius r. If the sphere has uniform density $\rho = \frac{M}{(4/3)\pi R^3}$, then $M_r = \frac{4}{3}\pi r^3 \rho = \frac{4}{3}\pi r^3 \frac{M}{(4/3)\pi R^3} = M \frac{r^3}{R^3}$. The force is then $F = G \frac{M_r m}{r^2} = G \frac{(M \frac{r^3}{R^3}) m}{r^2} = G \frac{M m r}{R^3}$. This matches the derivation in the NCERT for a point inside the Earth.
Which of the following values correctly represents the universal gravitational constant (G) as mentioned in the provided text?
The provided text in problem 7.17 and 7.19 explicitly states 'G = $6.67 \times 10^{-11} \text{ N m}^2 \text{ kg}^{-2}$'. The other options represent acceleration due to gravity, mass of Earth, and radius of Earth respectively.
The value of the universal gravitational constant, G, is used in determining the mass of the Earth. This determination is attributed to whose experiment, as per the text?
The text on page 133, under section 7.5, states: 'The measurement of G by Cavendish’s experiment (or otherwise), combined with knowledge of g and R_E enables one to estimate M_E from Eq. (7.12). This is the reason why there is a popular statement regarding Cavendish : “Cavendish weighed the earthâ€.'
According to the provided text, if the zero of potential energy is at infinity ($r \rightarrow \infty$), what is the nature of the gravitational potential energy of an object at a finite distance?
Points to Ponder, point 6, and page 135 state: 'Relative to infinity (i.e. if we presume that the potential energy of the object at infinity is zero), the gravitational potential energy of an object is negative.' and 'V = - $G m_1 m_2 / r$ (if we choose V = 0 as $r \rightarrow \infty$ )'. Since G, $m_1$, $m_2$, and r are positive, the expression - $G m_1 m_2 / r$ will always be negative.
The gravitational force between two ideal point masses is always along the line joining their centers. However, for two finite rigid bodies, the force is not necessarily along the line joining their center of mass. This statement is TRUE for which of the following scenarios to apply?
Points to Ponder, point 8, states: 'Although the gravitational force between two particles is central, the force between two finite rigid bodies is not necessarily along the line joining their centre of mass. For a spherically symmetric body however the force on a particle external to the body is as if the mass is concentrated at the centre and this force is therefore central.'
What is the gravitational potential energy (V) of two particles with masses $m_1$ and $m_2$ separated by a distance r, if potential energy is chosen to be zero at infinity?
The text on page 135 and Points to Ponder, point 5, explicitly states: 'The gravitational potential energy associated with two particles of masses $m_1$ and $m_2$ separated by distance by a distance r is given by $V = - G m_1 m_2 / r$ (if we choose V = 0 as $r \rightarrow \infty$ )'.
In the derivation of acceleration due to gravity 'g' on the Earth's surface (Eq. 7.12), which quantity represents the universal gravitational constant?
Equation (7.12) on page 133 is given as $g = G M_E / R_E^2$. In this equation, G is the universal gravitational constant, M_E is the mass of the Earth, and R_E is the radius of the Earth. F represents force, not a constant in this context.
Can a body be shielded from the gravitational influence of nearby matter by placing it inside a hollow sphere?
Points to Ponder, point 9, and Exercise 7.1 (a) explicitly state: 'Gravitational shielding is not possible.'
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