Physics NCERT Exemplar Solutions Class 11th Chapter Eight

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Answer-a, c, d

Explanation-due to the huge amount of charges on the sun and the earth electrostatics force of attraction will be large. Gravitational force is also attractive in nature have both forces will be added and obeys kepler's law also.

This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer-a, c, d

Explanation- G'=10G

Consider the diagram

Force on the objects due to the earth = $\frac{G^{\text{'}}Mm}{R^2}=\frac{10GMm}{R^2}$

= (10g)m= 10mg

Force on the objects due to the sun F= $\frac{GM\text{'}m}{r^2}=\frac{GMm}{10r^2}$

As r>>R  so F will be very small

So effect of sun will be neglected

Now g'=10g

Hence weight of person =10mg

So gravity pull on the person will increase, due to it walking on ground would be more difficult

Critical velocity V_c is proportional to g

So V_{c $\propto g$}

V'>g

V_c'>V_c hence rain will fall faster. To overcome the increased gravitational force of the earth the aeroplane will have to travel much faster.

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Answer-a, c

Explanation- as we know F= $\frac{GMm}{a^2}=\frac{m{v}^2}{a}$

V= orbital speed= $\frac{\sqrt[]{Gm}}{a}$

Time period of revolution of planet T = $\frac{2\pi a}{v}=\frac{2\pi a}{\frac{\sqrt[]{Gm}}{a}}$ = $\frac{2\pi a^2}{\sqrt[]{GM}}$

T² $\propto a^4$ ……….1

Hence orbit will be elliptical.

F= $\frac{GM}{a^3}m$ =g'm

It is clear from equation 1 that its path is parabola.

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Answer-a, c, d

Explanation- acceleration due to gravity at altitude g'= $\frac{g}{{\left(1+\frac{h}{R}\right)}^2}\approx g\left(1-\frac{2h}{R}\right)$

At depth d, g'=g (1-d/R)

In both cases value of g decreases

But in case of latitude the value of g increases when we increase $\varnothing$

$g_{\varnothing }=g-w^{2}R{cos}^2\varnothing$

also we conclude from the formula that it is independent upon mass.

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Answer-c

Explanation- force on B due to A = F_BA= $\frac{G\left(2Mm\right)}{{AB}^2}$

force on B due to C = F_BC= $\frac{G\left(Mm\right)}{{BC}^2}$

BC = 2AB

F_BC= $\frac{G\left(Mm\right)}{(2{AB)}^2}=\frac{G\left(Mm\right)}{4{AB}^2}$ BA

So it move towards BA

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Answer-d

Explanation- gravitational mass of proton is equivalent to its inertial mass and independent of presence neighbouring heavy objects.

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Answer-d

Explanation- asteroids are also being acted upon by central gravitational forces, hence they are moving in circular orbits like planets and obey Kepler's law.

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Answer-b

Explanation- as observed from the sun two types of forces are acting on the moon one is due to gravitational attraction between the sun and the moon and the other is due to gravitational attraction between the earth and the moon hence total force is not normal.

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Answer-c

Explanation- As the total energy of the earth satellite bounded system is negative . due to the viscous force acting on the satellite, energy decreases continuously and radius also decreases.

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Answer-a

Explanation- As the earth is revolving around the sun in a circular motion due to gravitational attraction. The force of attraction will be of radial nature and angle between them is zero so torque is also zero.