CBSE Class 9 Science Gravitation Worksheet Set A

 

Question. SI unit of G is
(a) \( N^2–m^2/kg \)
(b) \( N–m^2/kg \)
(c) \( N–m/kg \)
(d) \( N -m^2/kg^2 \)
Answer: D

Question. Choose the correct statement of the following:
(a) All bodies repel each other in this universe.
(b) Our earth does not behave like a magnet.
(c) Acceleration due to gravity is \( 8.9 \text{ m/s}^2 \).
(d) All bodies fall at the same rate in vacuum.
Answer: D

Question. Maximum weight of a body is
(a) at the centre of the earth
(b) inside the earth
(c) on the surface of the earth
(d) above the surface of earth
Answer: C

Question. If the distance between two masses be doubled, then the force between them will become
(a) \( 1/4 \) times
(b) \( 4 \) times
(c) \( 1/2 \) times
(d) \( 2 \) times
Answer: A

Question. A body falls freely towards the earth with
(a) uniform speed
(b) uniform velocity
(c) uniform acceleration
(d) none of these
Answer: C

Question. If the mass of a body is M on the surface of the earth, then its mass on the surface of the moon will be
(a) \( M/6 \)
(b) \( M \)
(c) \( M + 6 \)
(d) zero
Answer: B

Question. Weight
(a) is a vector quantity
(b) of a body in interplanetary space is maximum
(c) increases when the bodies go up
(d) none of these
Answer: A

Question. The value of g near the earth’s surface is
(a) \( 8.9 \text{ m/s}^2 \)
(b) \( 8.9 \text{ m/s} \)
(c) \( 9.8 \text{ m/s}^2 \)
(d) \( 9.8 \text{ m/s} \)
Answer: C

Question. A geostationary satellite
(a) moves faster than the near earth satellite
(b) has a time period less that of a near earth satellite
(c) revolves about the polar axis
(d) is stationary in space
Answer: C

Question. The force of gravitation between two bodies depend upon
(a) their separation
(b) gravitational constant
(c) product of their masses
(d) all of these
Answer: D

Question. When an object is thrown up, the force of gravity
(a) acts in the direction of the motion
(b) acts in the opposite direction of the motion
(c) remains constant as the body moves up
(d) increases as the body moves up
Answer: B

Question. The force of gravitation exists
(a) everywhere in the universe
(b) at the surface of the earth only
(c) inside the earth only
(d) at the surface of the moon only
Answer: A

Question. \( 1 \text{ kg wt} \) is equal to
(a) \( 9.8 \text{ N} \)
(b) \( 980 \text{ N} \)
(c) \( 98 \text{ N} \)
(d) none of these
Answer: A

Question. \( 1 \text{ kg wt} \) is equal to
(a) \( 980 \text{ dynes} \)
(b) \( 9.80 \text{ dynes} \)
(c) \( 98 \text{ dynes} \)
(d) none of these
Answer: A

Question. The value of G does not depend on
(a) nature of the interacting bodies
(b) size of the interacting bodies
(c) mass of the interacting bodies
(d) all of these
Answer: D

 

EXERCISE 

Question. If the distance between two masses be doubled, then the force between them will become
(a) \( 1/4 \) times
(b) \( 4 \) times
(c) \( 1/2 \) times
(d) \( 2 \) times
Answer: A

Question. How does the force of gravitation between two objects change when the distance between them is reduced to half?
(a) increases 4 times
(b) increases 2 times
(c) increases 16 times
(d) increases 32 times
Answer: D

Question. What happens to the gravitational force between two objects, if the mass of one object is doubled?
(a) increases 4 times
(b) increases 2 times
(c) increases 16 times
(d) increases 32 times
Answer: B

Question. What happens to the gravitational force between two objects, if the distance between the objects is tripled?
(a) becomes \( 1/9 \) times
(b) becomes \( 1/3 \) times
(c) becomes \( 1/27 \) times
(d) becomes 9 times
Answer: A

Question. What happens to the gravitational force between two objects, If the masses of both the objects are doubled?
(a) becomes 2 times
(b) becomes 8 times
(c) becomes \( 1/4 \) times
(d) becomes 4 times
Answer: D

Question. Calculate the gravitational force of attraction between a woman weighing 50 kg and her child of 12 kg separated by a distance of 2 m.
(a) \( 1.0 \times 10^{-10} \text{ N} \)
(b) \( 1.0 \times 10^{-11} \text{ N } 10^2 \)
(c) \( 1.0 \times 10^{-9} \text{ N} \)
(d) \( 1.0 \times 10^{-8} \text{ N} \)
Answer: D

Question. The gravitational force of attraction between two bodies is \( F_1 \). If the mass of each body is doubled and the distance between them is halved, then the gravitational force between them is \( F_2 \). Then
(a) \( F_1 = F_2 \)
(b) \( F_2 = 4F_1 \)
(c) \( F_2 = 8F_1 \)
(d) \( F_2 = 16F_1 \)
Answer: D

Question. Find the gravitational force between a body of 1 kg and the earth (mass of earth \( = 6 \times 10^{24} \text{ kg} \)). The radius of earth is \( 6.4 \times 10^6 \text{ m} \).
(a) \( 19.6 \text{ N} \)
(b) \( 9.8 \text{ N} \)
(c) \( 20 \text{ N} \)
(d) \( 36.08 \text{ N} \)
Answer: B

Question. Which of the following is correct:
(a) Moon has no atmosphere
(b) The tangential acceleration of a planet is zero
(c) Gravitational force is a medium dependent force
(d) Gravitational force is a conservative force
Answer: C

Question. The SI unit of g is
(a) \( \text{m}^2/\text{s} \)
(b) \( \text{m/s}^2 \)
(c) \( \text{s/m}^2 \)
(d) \( \text{m/s} \)
Answer: B

Question. The value of acceleration due to gravity near the earth’s surface is
(a) \( 8.9 \text{ m/s}^2 \)
(b) \( 8.9 \text{ m/s} \)
(c) \( 9.8 \text{ m/s}^2 \)
(d) \( 9.8 \text{ m/s} \)
Answer: C

Question. The relation between ‘g’ and ‘G’ is
(a) \( g = \frac{GM}{R^2} \)
(b) \( \frac{GR^2}{M} \)
(c) \( g = GMR^2 \)
(d) \( \frac{G}{MR^2} \)
Answer: A

Question. All bodies whether large or small fall with the
(a) Same force
(b) Same acceleration
(c) Same velocity
(d) Same momentum.
Answer: B

Question. In vaccum all freely falling objects
(a) Have the same speed
(b) Have the same velocity
(c) Have the same acceleration
(d) Have the same force.
Answer: C

Question. The ratio of \( g_{\text{moon}} \) to \( g_{\text{earth}} \) is
(a) \( 6 \)
(b) \( 1/6 \)
(c) \( 4 \)
(d) \( 1/4 \)
Answer: B

Question. The unit of the quantity g/G in SI will be
(a) \( \text{Kgm}^{–2} \)
(b) \( \text{mKg}^{–2} \)
(c) \( \text{m}^2\text{Kg}^{–1} \)
(d) \( \text{Kg}^2\text{m}^{–1} \)
Answer: A

Question. The ratio of SI units to CGS units of g is
(a) \( 10^2 \)
(b) \( 10 \)
(c) \( 10^{-1} \)
(d) \( 10^{-2} \)
Answer: A

Question. The acceleration due to gravity on the planet A is 9 times the acceleration due to gravity on planet B. A man can jump to a height of 2m on the surface of A. What is the height of jump by the same person on the planet B?
(a) \( 2/9 \text{ m} \)
(b) \( 18 \text{ m} \)
(c) \( 6 \text{ m} \)
(d) \( 2/3 \text{ m} \).
Answer: B

Question. The value of ‘g’ at poles is
(a) Greater than the value at the equator
(b) Less than the value at the equator
(c) Equal to the value at the equator
(d) None of these
Answer: A

Question. Two spheres of masses m and M are situated in air and the gravitational fore between them is F. The space around the masses is now filled with liquid of specific gravity 3. The gravitational force will now be
(a) \( 3F \)
(b) \( F \)
(c) \( F/3 \)
(d) \( F/9 \).
Answer: B

Question. The value of acceleration due to gravity on the surface of earth be denoted by g. If the radius of earth is 6400km, then what will be the acceleration due to gravity at a point 3200km above the surface of earth?
(a) \( g/9 \)
(b) \( 2g/9 \)
(c) \( 4g/9 \)
(d) \( g/2 \).
Answer: C

Question. The value of g on the earths surface is \( 980 \text{ cm/s}^2 \). Its value at a height of 64km from the earths surface is
(a) \( 960.40 \text{ cm/s}^2 \)
(b) \( 984.90 \text{ cm/s}^2 \)
(c) \( 982.45 \text{ cm/s}^2 \)
(d) \( 977.55 \text{ cm/s}^2 \)
Answer: A

Question. At what height above the earths surface does the acceleration due to gravity fall to 1% of its value at the earths surface?
(a) \( R \)
(b) \( 5R \)
(c) \( 10R \)
(d) \( 9R \).
Answer: D

Question. The value of g is with depth
(a) Increases
(b) Decreases
(c) Does not change
(d) increases or decreases
Answer: B

Question. A body is raised to a height h so that the force of gravity on the body is 1% of the value on the surface of Earth. If the radius of the Earth is 6400km, then the value of h is
(a) \( 57600 \text{ km} \)
(b) \( 5999 \text{ km} \)
(c) \( 9.8 \text{ km} \)
(d) \( 0.98 \text{ km} \)
Answer: A

Question. A man weights W on the surface of Earth. What is the weight at a height equal to R?
(a) \( W \)
(b) \( W/2 \)
(c) \( W/4 \)
(d) \( W/8 \)
Answer: C

Question. Radius of Earth is 6000km. Weight of a body on the surface of Earth is 120kg wt. If it is taken to a height of 2000km above the surface of Earth, its weight is
(a) \( 60 \text{ kg.wt} \)
(b) \( 40 \text{ kg.wt} \)
(c) \( 67.5 \text{ kg.wt} \)
(d) \( 47.5 \text{ kg.wt} \)
Answer: C

Question. The acceleration due to gravity is reduced to a value one-fourth of that on the surface of Earth at a height h where h is equal to \( xR_e \) (radius of Earth). The value of x is
(a) \( 1 \)
(b) \( 1/2 \)
(c) \( 1/3 \)
(d) \( 1/4 \)
Answer: A

Question. The value of ‘g’ at a certain height h above the free surface of Earth is \( x/4 \) where x is the value of ‘g’ at the surface of Earth. The height h is
(a) \( R \)
(b) \( 2R \)
(c) \( 3R \)
(d) \( 4R \)
Answer: A

Question. A body weights 63N on the surface of the Earth. At a height h above the surface of Earth, its weight is 28N while at a depth h below the surface of Earth, the weight is 31.5N. The value of h is
(a) \( 0.4R \)
(b) \( 0.5R \)
(c) \( 0.8R \)
(d) \( R \)
Answer: B

Question. The gravitational field due to a mass distribution is \( I = K/r^3 \) in the X-direction. (K is a constant). Taking the gravitational potential to be zero at infinity, its value at a distance x is
(a) \( K/x \)
(b) \( K/2x \)
(c) \( K/x^2 \)
(d) \( K/2x^2 \).
Answer: D

Question. The rotation period of earth satellite close to the surface of earth is 83 minutes. The time period of another earth satellite in an orbit at a distance of three earth radius from its surface will be
(a) 83 minutes
(b) \( 83 \times \sqrt{8} \) minutes
(c) 249 minutes
(d) 664 minutes.
Answer: D

Question. 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%, its speed will
(a) increase by 1%
(b) increase by 0.5%
(c) decrease by 1%
(d) decrease by 0.5%.
Answer: B

 

ADDITIONAL MCQs

 

Question. If g is the acceleration due to gravity on the earth’s surface, the gain in the potential energy of an object of mass m raised from the surface of earth to a height equal to the radius R of the earth is
(a) \( \frac{1}{2}mgR \)
(b) \( 2mgR \)
(c) \( mgR \)
(d) \( 1/4 \text{ mgR} \).
Answer: A

Question. The period of revolution of a certain planet in an orbit of radius R is T. Its period of revolution in an orbit of radius 4R will be
(a) \( 2T \)
(b) \( 2\sqrt{2}T \)
(c) \( 4T \)
(d) \( 8T \).
Answer: D

Question. If the radius of earth were to decrease by 1%, its mass remaining the same, the acceleration due to gravity on the surface of earth will
(a) increase by 1%
(b) increase by 2%
(c) decrease by 1%
(d) increase by 2%.
Answer: B

Question. According to Kepler’s laws, which of the following is correct?
(a) \( T \propto R^{3/2} \)
(b) \( T \propto R^3 \)
(c) \( T \propto R^{2/3} \)
(d) \( T \propto R^2 \).
Answer: A

Question. A space craft is launched in a circular orbit very close to Earth. What additional velocity should be given to the space craft so that it might escape the Earth’s gravitational pull? (Radius of the Earth \( = 6400 \text{ km} \); \( g = 9.8 \text{ m/s}^2 \))
(a) \( 11.2 \text{ km/s} \)
(b) \( 3.25 \text{ km/s} \)
(c) \( 85 \text{ km/s} \)
(d) \( 20.2 \text{ km/s} \).
Answer: B

Question. A body of mass m is placed on earth surface which is taken from earth surface to a height of h = 3R, then change in gravitational potential energy is
(a) \( \frac{1}{4}mgR \)
(b) \( \frac{2}{3}mgR \)
(c) \( \frac{3}{4}mgR \)
(d) \( \frac{1}{2}mgR \).
Answer: C

Question. A string has a tension T when it is holding a solid block below the surface of a liquid (liquid having density greater than that of solid) and the system is at rest. The tension in the string when the system has an acceleration a in upward direction is
(a) \( T(1+g/a) \)
(b) \( T(1-g/a) \)
(c) \( T(1+a/g) \)
(d) \( T(1-a/g) \).
Answer: C

Question. A wooden block with a coin placed on it’s top, floats in water as in the figure. The distance \( \ell \) and h are also shown there. After some time, the coin falls into the water, then
(a) \( \ell \) increases and h decreases
(b) \( \ell \) decreases and h increases
(c) both decrease
(d) both increases.
Answer: C

Question. An icecube has a stone frozen inside it. The cube floats in a beaker filled with water when the ice melts, then
(a) there is no change in level of water
(b) the water level decreases
(c) the water level increases
(d) the water level first increases then decreases.
Answer: B

Question. A piece of ice is floating in a jar containing water. When the ice melts, then the level of water.
(a) rises
(b) falls
(c) remains unchanged
(d) rises or falls depending upon the mass of ice
Answer: C

Question. Find the density of a block of wood that floats in water with 0.1 of its volume above water
(a) \( 0.9 \text{ g/cc} \)
(b) \( 0.9 \)
(c) \( 0.1 \text{ g/cc} \)
(d) \( 0.1 \)
Answer: A

Question. A body of volume 100 cc floats immersed completely in water contained in a jar. The mass of water and jar before immersion of the body was 700 g. After immersion mass of water and jar will be
(a) 500 g
(b) 700 g
(c) 100 g
(d) 800 g
Answer: D

Question. Two bodies of equal mass with volumes V and 2V are equalized on a balance. The large body is then immersed in oil of density \( \rho = 0.9 \text{ g/cc} \). What must be the density of the liquid in which the smaller body is simultaneously immersed so as not to disturb the equilibrium of the balance ?
(a) \( 0.9 \text{ g/cc} \)
(b) \( 1.8 \text{ g/cc} \)
(c) \( 0.45 \text{ g/cc} \)
(d) \( 1.35 \text{ g/cc} \)
Answer: B

Question. An empty balloon weighs \( W_1 \). If air equal in weight to W is pumped into the balloon, the weight of the balloon becomes \( W_2 \). Suppose that the density of air inside and outside the balloon is same then
(a) \( W_2 = W_1 + W \)
(b) \( W_2 = \sqrt{W_1W} \)
(c) \( W_2 = W_1 \)
(d) \( W_2 = W_1 – W \)
Answer: C

Question. A body of mass 120 kg and density \( 600 \text{ kg/m}^3 \) floats in water. What additional mass could be added to the body so that the body will just sink?
(a) 20 kg
(b) 80 kg
(c) 100 kg
(d) 120 kg
Answer: B

Question. By sucking through a straw, a student can reduce the pressure in his lungs to 750 mm of Hg (density \( = 13.6 \text{ g/cm}^3 \)). Using the straw, he can drink water from a glass upto a maximum depth of
(a) 10 cm
(b) 75 cm
(c) 13.6 cm
(d) 1.36 cm
Answer: C