Practice free NEET NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
A virtual image is formed when:
The NCERT text defines a virtual image as: 'The image is real if the rays actually converge to the point; it is virtual if the rays do not actually meet but appear to diverge from the point when produced backwards.'
A hollow spherical shell of uniform density attracts a point mass situated outside it. How does the shell's gravitational force on the point mass behave?
According to the NCERT text, 'The force of attraction between a hollow spherical shell of uniform density and a point mass situated outside is just as if the entire mass of the shell is concentrated at the centre of the shell.' This is a key result for spherical mass distributions.
What is the gravitational force experienced by a point mass situated inside a hollow spherical shell of uniform density?
The NCERT states, 'The force of attraction due to a hollow spherical shell of uniform density, on a point mass situated inside it is zero.' This is a fundamental property of gravitational fields within uniform spherical shells.
For a spherically symmetric body, how does the gravitational force on a particle external to it behave?
The NCERT explicitly mentions, '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.'
Consider a point mass $m$ placed inside a homogeneous solid sphere of mass $M$ and radius $R$, at a distance $r$ from its center ($r < R$). Which part of the sphere contributes to the gravitational force on $m$?
The NCERT states, 'If a particle is inside a homogeneous solid sphere, the force on the particle acts toward the centre of the sphere. This force is exerted by the spherical mass interior to the particle.' Gravitational forces from shells outside the particle's radius cancel out.
If the Earth is considered as a collection of concentric shells, and a point mass $m$ is situated at a depth $d$ below the surface (distance $r = R_E - d$ from the center), which shells exert a gravitational force on mass $m$?
The NCERT explains, 'For a point inside the earth, ...The point P lies outside the sphere of radius r. 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 surface.' Therefore, only the mass within the radius $r$ contributes.
If a point mass $m$ is at a distance $r$ from the center of a homogeneous solid sphere of mass $M$ and radius $R$ (where $r < R$), and Earth's uniform density $\rho$ is assumed, the mass of the sphere contributing to the force on $m$ ($M_r$) is given by:
Based on the NCERT text, 'On the other hand the mass of the sphere $M_r$ of radius $r$ is $\frac{4}{3}\pi r^3 \rho$'. This mass acts as if concentrated at the center.
For a point inside a homogeneous solid sphere of mass $M$ and radius $R$, at a distance $r$ from the center, the gravitational force $F$ on a particle of mass $m$ is proportional to:
From the NCERT explanation for a point inside the Earth (homogeneous solid sphere), the force is given by $F = G \frac{m M_r}{r^2}$. Since $M_r = \frac{4}{3} \pi r^3 \rho$, substituting this gives $F = G \frac{m (\frac{4}{3} \pi r^3 \rho)}{r^2} = G m (\frac{4}{3} \pi \rho) r$. Thus, the force is proportional to $r$.
Which of the following statements correctly describes the gravitational force from a hollow spherical shell of uniform density on an internal point mass?
The NCERT states, 'The force of attraction due to a hollow spherical shell of uniform density, on a point mass situated inside it is zero. Qualitatively, we can again understand this result. Various regions of the spherical shell attract the point mass inside it in various directions. These forces cancel each other completely.'
When considering the gravitational force exerted by the Earth on a point mass located at a point outside the Earth, how can the Earth's mass be regarded for calculating the force?
The NCERT states, 'at a point outside the earth, the gravitational force is just as if its entire mass of the earth is concentrated at its centre.' This applies for any spherically symmetric body.
Ready to ace NEET?
Free access · No credit card required
Yes. You can attempt every NEET question on this page for free without logging in, and check the correct answer with a detailed explanation instantly.
No account is required to attempt questions and view answers. A free account adds bookmarks, personal notes, and progress tracking.
The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.