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What is the source of centripetal force that a planet requires to revolve around the Sun? On what factors does that force depend?

Answer: Gravitational force is the source of centripetal force required to revolve around the sun. This force depends on the distance between... View Article

An apple falls from a tree because of gravitational attraction between the earth and apple. If F1 is the magnitude of force exerted by the earth on the apple and F2 is the magnitude of force exerted by apple on earth, then (a) F1 is very much greater than F2 (b) F2 is very much greater than F1 (c) F1 is only a little greater than F2 (d) F1 and F2 are equal

Answer: (d) F1 and F2 are equal Newton’s third law of motion states that when one body exerts a force on the other body, the first body... View Article

A girl stands on a box having 60 cm length, 40 cm breadth and 20 cm width in three ways. In which of the following cases, pressure exerted by the brick will be (a) maximum when length and breadth form the base (b) maximum when breadth and width form the base (c) maximum when width and length form the base (d) the same in all the above three cases

Answer: (b) maximum when breadth and width form the base Pressure is defined as the ratio of force to cross-section area. Pressure(P) =... View Article

An object weighs 10 N in air. When immersed fully in water, it weighs only 8 N. The weight of the liquid displaced by the object will be (a) 2 N (b) 8 N (c) 10 N (d) 12 N

Answer: (a) 2N Archimedes’ principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether... View Article

The weight of an object at the centre of the earth of radius R is (a) zero (b) infinite (c) R times the weight at the surface of the earth (d) 1/R2 times the weight at surface of the earth

Answer: (a) zero At the centre of the earth acceleration due to gravity is zero. Since weight is the product of mass and gravity. Weight of the... View Article

The force of attraction between two unit point masses separated by a unit distance is called (a) gravitational potential (b) acceleration due to gravity (c) gravitational field (d) universal gravitational constant

Answer: (d) universal gravitational constant The universal law of gravitation states that every particle attracts every other particle in the... View Article

The atmosphere is held to the earth by (a) gravity (b) wind (c) clouds (d) earth’s magnetic field

Answer: (a) gravity The universal law of gravitation states that every particle attracts every other particle in the universe with a force that... View Article

Two particles are placed at some distance. If the mass of each of the two particles is doubled, keeping the distance between them unchanged, the value of gravitational force between them will be (a) 14 times (b) 4 times (c) 12 times (d) unchanged

Answer: (b) 4 times The universal law of gravitation states that every particle attracts every other particle in the universe with a force that... View Article

The value of quantity G in the law of gravitation (a) depends on mass of earth only (b) depends on radius of earth only (c) depends on both mass and radius of earth (d) is independent of mass and radius of the earth

Answer: (d) is independent of mass and radius of the earth The universal law of gravitation states that every particle attracts every other... View Article

Law of gravitation gives the gravitational force between (a) the earth and a point mass only (b) the earth and Sun only (c) any two bodies having some mass (d) two charged bodies only

Answer: (d) two charged bodies only The universal law of gravitation states that every particle attracts every other particle in the universe... View Article

In the relation F = G (Mm/d², the quantity G (a) depends on the value of g at the place of observation (b) is used only when the earth is one of the two masses (c) is greatest at the surface of the earth (d) is universal constant of nature

Answer: (d) is universal constant of nature G is called as Newton’s constant. It is the force of gravity on a body. Value of G is 6.66x... View Article

An object is put one by one in three liquids having different densities. The object floats with 12 3 , and 1/9, 1/11, 1/7 parts of their volumes outside the liquid surface in liquids of densities d1, d2 and d3 respectively. Which of the following statement is correct? (a) d1> d2> d3 (b) d1> d2< d3 (c) d1< d2> d3 (d) d1< d2< d3

Answer: (d) d1< d2< d3 Buoyant Force is when a rigid object is submerged in a fluid, an upward force equal to the weight of the fluid that... View Article

A boy is whirling a stone tied with a string in an horizontal circular path. If the string breaks, the stone (a) will continue to move in the circular path (b) will move along a straight line towards the centre of the circular path (c) will move along a straight line tangential to the circular path (d) will move along a straight line perpendicular to the circular path away from the boy

Answer: (c) will move along a straight line tangential to the circular path At any instance of time objects in circular motion tend to be in... View Article

The gravitational force between two objects is F. If masses of both objects are halved without changing distance between them, then the gravitational force would become (a) F/4 (b) F/2 (c) F (d) 2 F

Answer: (a) F/4 The gravitational force between two objects is proportional to their masses and inversely proportional to the square of their... View Article

The value of acceleration due to gravity (a) is same on equator and poles (b) is least on poles (c) is least on equator (d) increases from pole to equator

Answer: (c) is least on the equator The value of acceleration due to gravity is least on the equator because the distance between the surface of... View Article

Two objects of different masses falling freely near the surface of moon would (a) have same velocities at any instant (b) have different accelerations (c) experience forces of same magnitude (d) undergo a change in their inertia

Answer:(a) have same velocities at any instant When an object is in free fall, its acceleration is solely determined by the acceleration due to... View Article

In the Gold foil experiment of Geiger and Marsden, that paved the way for Rutherford’s model of an atom, ~ 1.00% of the α-particles were found to deflect at angles > 50º. If one mole of α-particles were bombarded on the gold foil, compute the number of α-particles that would deflect at angles less than 500.

Answer: Total number of α particles used for bombardment = 1 mole 1 mole = 6.022×1023 particle number of α particles deflected... View Article

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