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Question Bank No: 3

1. A satellite is moving around the earth with speed v in a circular orbit of radius r. If the orbit radius is decreased by 1% , the speed of the satellite will

a)		Increased by 1%
b)		Increased by 0.5%
c)		Decreased by 1%
d)		Decreased by 0.5%

2. How much energy will be necessary for making a body of 500 kg escape from the earth? ( $g = 9.8 m / s^{2},$ radius of the earth = $6.4 \times 10^{8}$ m)

a)		About $9.8 \times 10^{6} J$
b)		About $6.4 \times 10^{8} J$
c)		About $3.1 \times 10^{10} J$
d)		About $27.4 \times 10^{12} J$

3. Two satellites are moving in orbits, $R_{1} > R_{2}$ ; then the velocities associated with them is

a)		$V_{1} < V_{2}$
b)		$V_{1} > V_{2}$
c)		$V_{1} = V_{2}$
d)		$V_{1} = {2 V}_{2}$

4. If g is the acceleration due to gravity on earth then increase in potential energy of a body of mass m upto a distance equal to the radius of the earth from the earth surface is

a)		$\frac{1}{2} mgR$
b)		2 mg R
c)		mg R
d)		$\frac{1}{4}$ mg R

5. 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)		1
b)		2
c)		3
d)		4

6. In a satellites if the time of revolution is T, then K.E is proportional to

a)		$1 / T^{2 / 3}$
b)		1/T
c)		$1 / T^{2}$
d)		$1 / T^{3}$

7. Two satellites A and B go round a planet P in circular orbits having radii 4 R and R respectively. If the speed of the satellites A is 3V, the speed of satellites B will be

a)		3V
b)		12V
c)		6V
d)		4/3 V

8. The length of a pendulums for a given time period is 'L'. If the pendulums is taken to a place where the acceleration due to gravity is doubled then for the time period to remain the same its length should be

a)		2L
b)		L
c)		L/2
d)		L/4

9. The weightlessness experienced while orbiting the earth in space ship is the result of

a)		acceleration
b)		zero activity
c)		inertia
d)		centre of gravity

10. Which of the following expression gives the minimum kinetic energy which a body of mass 'm' must be thrown in order that it escapes the gravitational field of the earth.

a)		GM/R
b)		2GM/R
c)		3GM/R
d)		GMm/R

11. If a seconds pendulums is taken from the earth to a planet whose radius is 4 times the radius of the earth but having the same density, the time period of the pendulums in the planet would be

a)		2 Sec
b)		4 Sec
c)		1 Sec
d)		0.5 Sec

12. The ratio of KE required to be given to the satellite to escape from earth to the kinetic energy required to be given to the satellite to revolve around the earth in an orbit just above the earth's surface is

a)		1:1
b)		2:1
c)		$\sqrt{2} : 1$
d)		4:1

13. Two satellites are in the parking orbits around the earth. Mass of one is 10 times that of the other. The ratio of their periods of evolution is

a)		1
b)		$\sqrt{10}$
c)		10
d)		100

14. If the earth suddenly shrinks to half of its present radius, the acceleration due to gravity will be

a)		g/2
b)		4g
c)		g/4
d)		2g

15. The escape velocity of a projectile from earth is approximately

a)		7 km/s
b)		112 km/sec
c)		11.2 km/sec
d)		1.1 km/sec

16. Gravitational mass is proportional to gravitational

a)		field
b)		force
c)		intensity
d)		momentum

17. The weight of an astronauts in an artificial satellite revolving around the earth is

a)		more than that on the earth
b)		less than that on the earth
c)		equal to that on the earth
d)		zero

18. The orbital velocity for an earth satellite near the surface of the earth is 7 km/sec. If the radius of the orbit is 4 times the radius of the earth, its orbital velocity would be

a)		3.5 km/sec
b)		7 km/sec
c)		$7 \sqrt{2}$ km/sec
d)		14 km/sec

19. A spaceship moves from earth to moon and back. The greatest energy required for the spaceship is to overcome the difficulty in

a)		entering the earth's gravitational field
b)		take off form earth's field
c)		take off from lunar surface
d)		entering in the moon's lunar surface

20. The period of revolution of a certain planet in an orbit of radius R is 'T'. The period of revolution in an orbit of radius 4R will be

a)		2T
b)		$2 \sqrt{2 T}$
c)		4T
d)		8T

21. A satellite is revolving around the sun in a circular orbit with uniform velocity V. If the gravitational force suddenly disappears, the velocity of the satellite will be

a)		zero
b)		V
c)		2V
d)		3V

22. In a gravitational field, work done in transporting mass from one point to another depends upon

a)		the end position
b)		the distance between them
c)		actual point of motion
d)		velocity of transport

23. If the radius of earth is reduced to 20%, keeping mass constant, then weight of the body on its surface

a)		decreases
b)		increases
c)		remains same
d)		is more than that at pole

24. A body weighs 72N on the surface of the earth. What is the gravitational force on it due to earth at a height equal to half the radius of the earth from the surface?

a)		72N
b)		28N
c)		16N
d)		32N

25. In a satellite, if the time of resolution is T, then Kinetic energy is proportional to

a)		$\frac{1}{T^{2 / 3}}$
b)		$\frac{1}{T}$
c)		$\frac{1}{T^{2}}$
d)		$\frac{1}{T^{3}}$

26. The earth revolves round the sun in one year, if the distance between them becomes double, the new period of evolution will be

a)		(1/2) year
b)		$2 \sqrt{2}$ year
c)		4 year
d)		8 year

27. The rotation period of an earth satellite close to the surface of the earth is 83 minutes. The satellite in an orbit at a distance of 3 times earth radius from its surface will be

a)		83 minutes
b)		$83 \times \sqrt{8}$ minutes
c)		664 minutes
d)		249 minutes

28. Two planets of radii $R_{1}$ and $R_{2}$ are made from the same material. The ratio of the acceleration due to gravity $G_{1} / G_{2}$ at the surface of two planets is

a)		$R_{1} / R_{2}$
b)		$R_{2} / R_{1}$
c)		${(R}_{1} / R_{2})^{2}$
d)		${(R}_{2} / R_{1})^{2}$

29. Intensity of gravitational field is of earth is minimum at

a)		poles
b)		equator
c)		centers of earth
d)		same everywhere

30. The time period of a satellite in a circular orbit of radius R is T. The radius of the orbit in which time period is 8T is

a)		2R
b)		3R
c)		4R
d)		5R

31. A missile is launched with a velocity less than the escape velocity . The sum of its kinetic and potential energy is

a)		positive
b)		negative
c)		zero
d)		may be positive or negative depending upon the initial velocity

32. Who among the following gave first, the experimental value of 'G'?

a)		Cavendish
b)		Copernicus
c)		Brook Teyler
d)		Albert Einstene

33. If a planet consists of a satellite whose mass and radius were both half that of the earth, the acceleration due to gravity at its surface would be

a)		$4.9 m / s^{2}$
b)		$9.8 m / s^{2}$
c)		$19.6 m / s^{2}$
d)		$29.4 m / s^{2}$

34. The radii of the circular orbits of two satellites around the earth are in the ratio 1:4. The ratio of their respective period of revolution is

a)		1:4
b)		4:1
c)		1:8
d)		8:1

35. The time period of a seconds pendulum in a satellite is

a)		zero
b)		2
c)		infinity
d)		1

36. The periodic time in a communication satellite is

a)		6 hours
b)		12 hours
c)		15 hours
d)		24 hours