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### Newton's Law of Motion (Objective Type Questions)

(1)Friction force can be reduced to great extent by
a. lubricating the two moving parts
b. using ball bearing between two moving parts
c. introducing a thin cushion of air maintained between two relatively moving surfaces
d. all the above

(2) Force exerted on a body can change its
a. kinetic energy
b. direction of motion
c. speed
d. momentum

(3) A block is released from the top of a smooth inclined plane. Another block of same mass is allowed to fall freely from the top of the inclined plane. Both blocks reach the bottom of the plane
a. with equal speed
b. in equal interval of time
c. with equal kinetic energy
d. with equal momentum

(4) Which of the following expression does not represent the force acting on the body of mass m
a. GMem/(Re)2
b. ma
c. μN
d. 6ηπrv

(5) A body of mass m is resting on the floor. A minimum amount of force is applies on the body and the force continues to act on the body as it moves. If coefficent of static and dynamic friction are 0.4 and 0.3 resp. then the acceleration of the body is
a. 0
b. 3.98
c. 0.98
d. 4.98

(1) d.
(2) a, b, c, d
(3) a and c
(4) d
(5) c

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### Electrostatic questions for board exams

Q.1 A certain region has spherical symmetry of electric field. Name the charge distribution producing such a field.

Q.2 Represent graphically the variation of electric field with distance, for a uniformly charged sphere.

Q.3 How will the radius of a flexible ring change if it is given positive charge?

Q.4 Five Charges of equal amount (q) are placed at five corners of a regular hexagon of side 20 cm. What will be the value of sixth charge placed at sixth corner of the hexagon so that the electric field at the centre of hexagon is zero ?.

Q.5 Two conducting spheres of radii r1 & r2 are at same potential. What is the ratio of charges on the spheres?

Q.7 An electric charge q is placed at one of the corner of a cube of side ‘a’. What will be the electric flux through its one of the face?

Q.8 A charge Q is divided in two parts q and Q - q separated by a distance R. If force between the two charges is maximum, find the relationship between q & Q.

Q.9 If 20 drops of same size, each having the same charge, coalesce to form a bigger drop. How will the following vary with respect to single small drop?
(i)Total charge on bigger drop
(ii) Potential on the bigger drop
(iii) The capacitance on the bigger drop
Consider the drops to have spherical symmetry.

Q.10 Work done to move a charge along a closed path inside an electric field is always zero, using this fact, prove that it is impossible to produce an electric field in which all limes of force would be parallel lines and density of their distribution would constantly increase in a direction perpendicular to the lines of force.
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