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# NEET Physics  Gravitation  Practice Q & A

1. If ‘r’ represents the radius of the orbit of a satellite of mass ‘m’ moving round a planet of mass ‘M’, the velocity of the satellite is given by

 v2 = $\dfrac{gM}{r}$ v2 = $\dfrac{GMm}{r}$ v = $\sqrt{\dfrac{GM}{r}}$ v = $\dfrac{GM}{r^{2}}$

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2. When the planet comes nearer the sun moves

 fast slow constant at every point none of the above

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3. Kepler’s second law regarding constancy of arial velocity of a planet is a consequence of the law of conservation of

 energy angular momentum linear momentum none of these

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4. The relation between escape velocity and orbit velocity is

 ve = $\sqrt{2v}_{orb}$ ve = $\dfrac{1}{\sqrt{2}}v_{orb}$ ve = $2v_{orb}$ ve = $\sqrt{3}v_{orb}$

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5. A geostationary satellite is orbiting the earth at a height of 6R above the surface of the earth, R being the radius of the earth. The time period of another satellite at a height of 2.5 R from the surface of earth is

 6$\sqrt{2}$ hr 6 hr 5$\sqrt{2}$ hr 10 hr

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6. The distance of Neptune and Saturn from the sun are nearly 1013 m and 1012 m respectively. Assuming that they move in circular orbits, their periodic times would be in the ratio of

 10 100 10 $\sqrt{10}$ 1000

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7. Imagine a light planet revolving around a very massive star in a circular orbit of radius R with a period of revolution T. If the gravitational force of attraction between the planet and the star is proportional to R-5/2 then

 T2 \propto R2 T2 \propto R7/2 T2 \propto R3/2 T2 \propto R3

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8. The acceleration due to gravity g and mean density of the earth ρ are related by which of
the following relation? Where g is gravitational constant and R is radius of the earth

 ρ = $\dfrac{4\pi gR^{2}}{3G}$ ρ = $\dfrac{4\pi gR^{3}}{3G}$ ρ = $\dfrac{3g}{4\pi GR}$ ρ = $\dfrac{3g}{4\pi GR^{3}}$

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9. If the earth is 1/4th of its present distance from the sun, the duration of the year would be

 1/4 of the present year 1/6 of the present year 1/8 of the present year 1/16 of the present year

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10. A planet has twice the radius but the mean density is 1/4th as compared to earth. What is the radio of the escape velocity from the earth to that from the planet?

 3 : 1 1 : 2 1 : 1 2 : 1

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