-1<\/sup><\/p>\nQuestion 16.
\nForce is measured based on:
\n(a) Newton\u2019s first law
\n(b) Newton\u2019s second law
\n(c) Newton\u2019s third law
\n(d) All the above
\nAnswer:
\n(b) Newton\u2019s second law<\/p>\n
Question 17.
\nForce measures rate of change of:
\n(a) acceleration
\n(b) velocity
\n(c) momentum
\n(d) distances
\nAnswer:
\n(c) momentum<\/p>\n
Question 18.<\/p>\n
The rotating or turning effect of a force about a fixed point or fixed axis is called _____ .
\n(a) Force
\n(b) momentum
\n(c) torque
\n(d) couples.
\nAnswer:
\n(c) torque<\/p>\n
Question 19.
\nThe physical quantity which is equal to the rate of change of momentum is:
\n(a) displacement
\n(b) acceleration
\n(c) force
\n(d) impulse
\nAnswer:
\n(c) force<\/p>\n
Question 20.
\nThe momentum of a massive object at rest is:
\n(a) very large
\n(b) very small
\n(c) zero
\n(d) infinity
\nAnswer:
\n(c) zero<\/p>\n
Question 21.
\nThe velocity which is sufficient to just escape from the gravitational pull of the earth is _____ .
\n(a) drift velocity
\n(b) escape velocity
\n(c) gradual velocity
\n(d) final velocity.
\nAnswer:
\n(b) escape velocity<\/p>\n
Question 22.
\nA force applied on an object is equal to:
\n(a) product of mass and velocity
\n(b) sum of mass and velocity of an object
\n(c) product of mass and acceleration
\n(d) sum of mass and acceleration
\nAnswer:
\n(c) product of mass and acceleration<\/p>\n
Question 23.
\nAction and reaction do not balance each other because they:
\n(a) act on the same body
\n(b) do not act on the same body
\n(c) are in opposite direction
\n(d) are unequal
\nAnswer:
\n(b) do not act on the same body<\/p>\n
<\/p>\n
Question 24.
\nThe value of variation of accelaration due to gravity (g) is ______ at the centre of the earth.
\n(a) one
\n(b) zero
\n(c) \u221e
\n(d) \\(\\frac{1}{\\infty}\\).
\nAnswer:
\n(b) zero<\/p>\n
Question 25.
\nAction and reaction forces are:
\n(a) equal in magnitude
\n(b) equal in direction
\n(c) opposite in direction
\n(d) both equal in magnitude and opposite in direction
\nAnswer:
\n(d) both equal in magnitude and opposite in direction<\/p>\n
Question 26.
\nIf mass of a body is doubled then its acceleration becomes:
\n(a) halved
\n(b) doubled
\n(c) thrice
\n(d) zero
\nAnswer:
\n(a) halved<\/p>\n
Question 27.
\nThe principle involved in the working of a jet plane is:
\n(a) Newton\u2019s first law
\n(b) Conservation of momentum
\n(c) Law of inertia
\n(d) Newton\u2019s second law
\nAnswer:
\n(b) Conservation of momentum<\/p>\n
Question 28.
\n_____ of a body is defined as the quantity of matter contained in the object.
\n(a) weight
\n(b) mass
\n(c) force
\n(d) momentum.
\nAnswer:
\n(b) mass<\/p>\n
Question 29.
\nA gun gets kicked back when a bullet is fired. It is a good example of Newton’s:
\n(a) gravitational law
\n(b) first law
\n(c) second law
\n(d) third law
\nAnswer:
\n(d) third law<\/p>\n
Question 30.
\nTo change the state or position of an object force is essential.
\n(a) balanced
\n(b) unbalanced
\n(c) electric
\n(d) elastic
\nAnswer:
\n(b) unbalanced<\/p>\n
Question 31.
\nWhen a bus starts suddenly the passengers in the standing position are pushed backwards, this action is due to:
\n(a) first law of motion
\n(b) second law of motion
\n(c) third law of motion
\n(d) conservation of momentum
\nAnswer:
\n(a) first law of motion<\/p>\n
Question 32.
\nWhen a body at rest breaks into two pieces of equal masses, then the parts will move:
\n(a) in same direction
\n(b) along different directions
\n(c) in opposite directions with unequal speeds
\n(d) in opposite directions with equal speeds
\nAnswer:
\n(d) in opposite directions with equal speeds<\/p>\n
Question 33.
\nThe principle of function of a jet aeroplane is based on:
\n(a) first law of motion
\n(b) second law of motion
\n(c) third law of motion
\n(d) all the above
\nAnswer:
\n(c) third law of motion<\/p>\n
Question 34.
\nWhich of the following has the largest inertia?
\n(a) pin
\n(b) book
\n(c) pen
\n(d) table
\nAnswer:
\n(d) table<\/p>\n
<\/p>\n
Question 35.
\nAn athlete runs a long path before taking a long jump to increase:
\n(a) energy
\n(b) inertia
\n(c) momentum
\n(d) force
\nAnswer:
\n(c) momentum<\/p>\n
Question 36.
\nThe weight of a person is 50 kg. The weight of that person on the surface
\n(a) 50 N
\n(b) 35 N
\n(c) 380 N
\n(d) 490 N
\nAnswer:
\n(d) 490 N<\/p>\n
Question 37.
\nWhich is incorrect statement about the action and reaction referred to Newton’s third law of motion?
\n(a) They are equal
\n(b) They are opposite
\n(c) They act on the same object
\n(d) They act on two different objects
\nAnswer:
\n(c) They act on the same object<\/p>\n
Question 38.
\nThe tendency of a force to rotate a body about a given axis is called:
\n(a) turning effect of a force
\n(b) moment of force
\n(c) torque
\n(d) all the above
\nAnswer:
\n(d) all the above<\/p>\n
Question 39.
\nThe magnitude of the moment of force is:
\n(a) product of force and the perpendicular distance
\n(b) product of force and velocity
\n(c) ratio of force to the acceleration
\n(d) ratio of force to the perpendicular distance
\nAnswer:
\n(a) product of force and the perpendicular distance<\/p>\n
Question 40.
\nIf the force rotates the body in the anticlockwise direction, then the moment is called:
\n(a) clockwise moment
\n(b) anticlockwise moment
\n(c) couple
\n(d) torque
\nAnswer:
\n(b) anticlockwise moment<\/p>\n
Question 41.
\nAnticlockwise moment is:
\n(a) positive
\n(b) negative
\n(c) opposite
\n(d) zero
\nAnswer:
\n(a) positive<\/p>\n
Question 42.
\nClockwise moment or torque is:
\n(a) zero
\n(b) always one
\n(c) negative
\n(d) positive
\nAnswer:
\n(c) negative<\/p>\n
Question 43.
\nSI unit of moment of force is:
\n(a) Nm-2<\/sup>
\n(b) Nm-1<\/sup>
\n(c) Ns
\n(d) Nm
\nAnswer:
\n(d) Nm<\/p>\nQuestion 44.
\nMoment of force produces:
\n(a) acceleration
\n(b) linear motion
\n(c) velocity
\n(d) angular acceleration
\nAnswer:
\n(d) angular acceleration<\/p>\n
Question 45.
\nTwo equal and opposite forces whose lines of action do not coincide are said to constitute a:
\n(a) couple
\n(b) torque
\n(c) unlike force
\n(d) parallel force
\nAnswer:
\n(a) couple<\/p>\n
<\/p>\n
Question 46.
\nCouple produces:
\n(a) translatory motion
\n(b) rotatory motion
\n(c) translatory as well as rotatory motion
\n(d) neither translatory nor rotatory
\nAnswer:
\n(b) rotatory motion<\/p>\n
Question 47
\n……. is an example of couple.
\n(a) opening or closing a tap
\n(b) turning of a key in a lock
\n(c) steering wheel of car
\n(d) all the above
\nAnswer:
\n(d) all the above<\/p>\n
Question 48.
\nForce of attraction between any two objects in the universe is called:
\n(a) gravitational force
\n(b) mechanical force
\n(c) magnetic force
\n(d) electrostatic force
\nAnswer:
\n(a) gravitational force<\/p>\n
Question 49.
\nUniversal law of gravitation was given by:
\n(a) Archimedes
\n(b) Aryabhatta
\n(c) Kepler
\n(d) Newton
\nAnswer:
\n(d) Newton<\/p>\n
Question 50.
\nThe force of gravitation between two bodies does not depend on:
\n(a) product of their masses
\n(b) their separation
\n(c) sum of their masses
\n(d) gravitational constant
\nAnswer:
\n(c) sum of their masses<\/p>\n
Question 51.
\nLaw of gravitation is applicable to:
\n(a) heavy bodies only
\n(b) small sized objects
\n(c) light bodies
\n(d) objects of any size
\nAnswer:
\n(d) objects of any size<\/p>\n
Question 52.
\nThe value of gravitational constant (G) is:
\n(a) different at different places
\n(b) same at all places in the universe
\n(c) different at all places of earth
\n(d) same only at all the places of earth
\nAnswer:
\n(b) same at all places in the universe<\/p>\n
Question 53.
\nThe unit of gravitational constant is:
\n(a) Nm\u00b2 kg
\n(b) kgms-2<\/sup>
\n(c) Nm\u00b2 kg-2<\/sup>
\n(d) ms-2<\/sup>
\nAnswer:
\n(c) Nm\u00b2 kg-2<\/sup><\/p>\n<\/p>\n
Question 54.
\nThe weight of an object is:
\n(a) the quantity of matter it contains
\n(b) its inertia
\n(c) same as its mass
\n(d) the force with which it is attracted by the earth
\nAnswer:
\n(d) the force with which it is attracted by the earth<\/p>\n
Question 55.
\nIn vacuum, all freely failing objects have the same:
\n(a) speed
\n(b) velocity
\n(c) force
\n(d) acceleration
\nAnswer:
\n(d) acceleration<\/p>\n
Question 56.
\nThe acceleration due to gravity:
\n(a) has the same value everywhere in space
\n(b) has the same value everywhere on earth
\n(c) varies with the latitude on earth
\n(d) is greater on moon due to its smaller diameter
\nAnswer:
\n(c) varies with the latitude on earth<\/p>\n
Question 57.
\nWhen an object is thrown up, the force of gravity:
\n(a) is opposite to the direction of motion
\n(b) is in the same direction as direction of motion
\n(c) decreases as it rises up
\n(d) increases as it rises up
\nAnswer:
\n(a) is opposite to the direction of motion<\/p>\n
Question 58.
\nThe SI unit of acceleration due to gravity ‘g’ is:
\n(a) ms-1<\/sup>
\n(b) ms
\n(c) ms-2<\/sup>
\n(d) ms\u00b2
\nAnswer:
\n(c) ms-2<\/sup><\/p>\nQuestion 59.
\nWhat happens to the value of ‘g’ as we go higher from surface of earth?
\n(a) decreases
\n(b) increases
\n(c) no change
\n(d) zero
\nAnswer:
\n(a) decreases<\/p>\n
Question 60.
\nMass of a body on moon is:
\n(a) the same as that on the earth
\n(b) \\(\\frac{1}{6}\\)th of that at the surface of the earth
\n(c) 6 times as that on the earth
\n(d) none of these
\nAnswer:
\n(a) the same as that on the earth<\/p>\n
Question 61.
\nAt which place is the value of ‘g’ is zero?
\n(a) at poles
\n(b) at centre of the earth
\n(c) at equator
\n(d) above the earth
\nAnswer:
\n(b) at centre of the earth<\/p>\n
Question 62.
\nThe weight of the body is maximum:
\n(a) at the centre of the earth
\n(b) on the surface of earth
\n(c) above the surface of earth
\n(d) none of the above
\nAnswer:
\n(b) on the surface of earth<\/p>\n
Question 63.
\nA rock is brought from the surface of the moon to the earth, then its:
\n(a) weight will change
\n(b) mass will change
\n(c) both mass and weight will change.
\n(d) mass and weight will remain the same
\nAnswer:
\n(a) weight will change<\/p>\n
Question 64.
\nWhy is the acceleration due to gravity on the surface of the moon is lesser than that on the surface of earth?
\n(a) because mass of moon is less
\n(b) radius of moon is less
\n(c) mass and radius of moon is large
\n(d) mass and radius of moon is less
\nAnswer:
\n(d) mass and radius of moon is less<\/p>\n
<\/p>\n
Question 65.
\nif the distance between two bodies is doubled, then the gravitational force between them is:
\n(a) halved
\n(b) doubled
\n(c) reduced to one-fourth
\n(d) increased by one fourth
\nAnswer:
\n(c) reduced to one-fourth<\/p>\n
Question 66.
\nThe unit newton can also be written as:
\n(a) kgm
\n(b) kgms-1<\/sup>
\n(c) kgms-2<\/sup>
\n(d) kgm-2<\/sup>s
\nAnswer:
\n(c) kgms-2<\/sup><\/p>\nQuestion 67.
\nA bus starts for rest and moves after 4 seconds. Its velocity is 100 ms 1. Its uniform acceleration is:
\n(a) 10 ms-2<\/sup>
\n(b) 25 ms-2<\/sup>
\n(c) 400 ms-2<\/sup>
\n(d) 2.5 ms-2<\/sup>
\nAnswer:
\n(b) 25 ms-2<\/sup><\/p>\nQuestion 68.
\nA body of mass 10 kg increases its velocity from 2 m\/s to 8 m\/s within 4 second by the application of a constant force. The magnitude of the applied force is:
\n(a) 1.5 N
\n(b) 30 N
\n(c) 15 N
\n(d) 150 N
\nAnswer:
\n(c) 15 N<\/p>\n
Question 69.
\nThe moment of force in clockwise direction is the moment in the anticlockwise direction.
\n(a) equal to
\n(b) lesser than
\n(c) greater than
\n(d) none
\nAnswer:
\n(a) equal to<\/p>\n
Question 70.
\nWhich one of the following is scalar quantity?
\n(a) momentum
\n(b) moment of force
\n(c) speed
\n(d) velocity
\nAnswer:
\n(c) speed<\/p>\n
Question 71.
\nWhich of the following changes the direction of motion of a body?
\n(a) momentum
\n(b) force
\n(c) energy
\n(d) mass
\nAnswer:
\n(b) force<\/p>\n
Question 72.
\nWhen one makes a sharp turns while driving a car he tends to lean sideways due to:
\n(a) inertia
\n(b) inertia of rest
\n(c) inertia of motion
\n(d) inertia of direction
\nAnswer:
\n(d) inertia of direction<\/p>\n
Question 73.
\nThe unit of momentum is:
\n(a) kg m
\n(b) m\/s\u00b2
\n(c) kg m\/s
\n(d) joule
\nAnswer:
\n(c) kg m\/s<\/p>\n
<\/p>\n
Question 74.
\nMoment of a force is given by \u03c4 =
\n(a) \\(\\frac{F}{d}\\)
\n(b) F \u00d7 2d
\n(c) \\(\\frac{F}{d}\\)
\n(d) F \u00d7 d
\nAnswer:
\n(d) F \u00d7 d<\/p>\n
Question 75.
\nWhich of the following work on the principle of torque?
\n(a) Gears
\n(b) Seasaw
\n(c) steering wheel
\n(d) all the above
\nAnswer:
\n(d) all the above<\/p>\n
Question 76.
\nThe SI unit of gravitational constant
\n(a) Nm\u00b2\/g
\n(b) Nm\u00b2kg\u00b2
\n(c) Nm\u00b2\/g-2<\/sup>
\n(d) Nmkg
\nAnswer:
\n(c) Nm\u00b2\/g-2<\/sup><\/p>\nQuestion 77.
\nWhat is the value of gravitational constant?
\n(a) 6.674 \u00d7 10-11<\/sup> Nm\u00b2\/g-2<\/sup>
\n(b) 9.8 \u00d7 10-11<\/sup> Nm\u00b2\/g-2<\/sup>
\n(c) 6.647 \u00d7 10-11<\/sup> Nm\u00b2\/g-2<\/sup>
\n(d) 13.28 \u00d7 10-11<\/sup> Nm\u00b2\/g-2<\/sup>
\nAnswer:
\n(a) 6.674 \u00d7 10-11<\/sup> Nm\u00b2\/g-2<\/sup><\/p>\nQuestion 78.
\nThe value of mass of the Earth is:
\n(a) 6.972 \u00d7 1024<\/sup> kg
\n(b) 6.792 \u00d7 1024<\/sup> kg
\n(c) 5.972 \u00d7 1024<\/sup> kg
\n(d) 2.936 \u00d7 1024<\/sup> kg
\nAnswer:
\n(c) 5.972 \u00d7 1024<\/sup> kg<\/p>\nQuestion 79.
\nAt poles of the Earth, weight of the body is:
\n(a) minimum
\n(b) maximum
\n(c) zero
\n(d) infinity
\nAnswer:
\n(b) maximum<\/p>\n
Question 80.
\nWhere will the value of acceleration due to gravity be minimum?
\n(a) poles of the earth
\n(b) centre of the earth
\n(c) equator of the earth
\n(d) space
\nAnswer:
\n(d) space<\/p>\n
Question 81.
\nWhen an elevator is at rest:
\n(a) Apparent weight is greater than the actual weight
\n(b) Apparent weight is less than the actual weight
\n(c) Apparent weight is equal to the actual weight
\n(d) None of the above
\nAnswer:
\n(c) Apparent weight is equal to the actual weight<\/p>\n
Question 82.
\nIn a lift, apparent weight of a body is equal to zero when the lift is;
\n(a) at rest
\n(b) moving upwards
\n(c) moving downwards
\n(d) falling down freely
\nAnswer:
\n(d) falling down freely<\/p>\n
Question 83.
\nWhen the lift is moving upward with an acceleration ‘o’ the apparent weight of the body is:
\n(a) lesser than actual weight
\n(b) greater than actual weight
\n(c) equal to actual weight
\n(d) zero
\nAnswer:
\n(b) greater than actual weight<\/p>\n
Question 84.
\nWhen an elevator is moving downward, the apparent weight of a person who is in that elevator is:
\n(a) maximum
\n(b) zero
\n(c) minimum
\n(d) infinity
\nAnswer:
\n(c) minimum<\/p>\n
Question 85.
\nWhich law helps to predict the path of the astronomical bodies?
\n(a) Newton\u2019s law of motion
\n(b) Newton\u2019s law of gravitation
\n(c) Newton\u2019s law of cooling
\n(d) Pascal\u2019s law
\nAnswer:
\n(b) Newton\u2019s law of gravitation<\/p>\n
<\/p>\n
II. Fill in the blanks.<\/span><\/p>\n1. If force – mass \u00d7 acceleration, then momentum = ………
\n2. If liquid hydrogen is for rocket, then …….. is for MRI.
\n3. Inertia: (f) Mass then momentum: ……… Recoil of the gun: (ii) Newton’s third law: then flight of Jet Planes and Rockets: ………
\n4. Newton’s first law of motion: definition of force and inertia then Newton’s third law of motion: ….(i)….. while Newton’s second law of motion: ……(ii)…….
\n5. Newton’s first law: qualitative definition of force Newton’s second law: …..(i)…… The value of g: 9.8 ms-2 then Gravitational constant: …..(ii)……
\n6. Force: vector then momentum: …….(i)……. Balanced force: resultant of the two forces is zero then……(ii)…….. : resultant forces are responsible for change in position or state.
\n7. Momentum is the product of …….. and …….
\n8. To produce an acceleration of 1 m\/s\u00b2 in an object of mass 1 kg. The force required is ……… and for 3 kg of mass to produce same acceleration, the force required is ……….
\n9. Two or more forces are acting in an object and does not change its position, the forces are ………. and it is essential to act some ………. force, to change the state or position of an object.
\n10. ……… deals with bodies that are at rest under the action of force.
\n11. A branch of mechanics that deals with the motion of the bodies considering the cause of motion is called ………
\n12. If m is the mass of a body moving with velocity v then its momentum is given by P = ……..
\n13. A system of forces can be brought to equilibrium by applying ………. in opposite direction.
\n14. Torque is a ……… quantity.
\n15. Steering wheel transfers a torque to the wheels with ………..
\n16. The mathematical form of the principle of moments is ………..
\n17. Change in momentum takes place in the ………. of ………
\n18. 1 Newton = ……..
\n19. If a force F acts on a body for a time t’s then the impulse is ………
\n20. 1 kg f = ………
\n21. The force of attraction between two objects is directly proportional to the product of their ……. and inversely proportional to the square of the ………. between them.
\n22. The value of g varies with ……… and ………
\n23. The value of gravitational constant is ……… at all places but the value of acceleration due to gravity ………..
\n24. The relation between g and G is ………
\nAnswer:
\n1. mass \u00d7 velocity
\n2. liquid helium
\n3. (i) Mass and velocity, (ii) Law of conservation of momentum
\n4. (i) Law of conservation of momentum, (ii) Measure of force
\n5. (i) Quantitative definition of force, (ii) 6.673 \u00d7 10-11<\/sup> Nm\u00b2kg-2<\/sup>
\n6. (i) vector, (ii) imbalanced force
\n7. mass, velocity
\n8. 1 N, 3 N
\n9. balanced, unbalanced
\n10. Statics
\n11. kinetics
\n12. mv
\n13. equilibriant
\n14. vector
\n15. less effort
\n16. F1<\/sub> \u00d7 d1<\/sub> = F2<\/sub> \u00d7 d2<\/sub>
\n17. direction, force
\n18. 105<\/sup> dyne
\n19. I = F \u00d7 t
\n20. 9.8 N
\n21. masses, distance
\n22. altitude, depth
\n23. same, differs
\n24. g = \\(\\frac{GM}{R^2}\\)<\/p>\nIII. State whether the following statements are true or false. Correct the statement if it is false.<\/span><\/p>\n1. Newton’s first law explains inertia:
\n2. If a motion depends on force then it is called as natural motion.
\n3. The resistance of a body to change its state of motion is known as inertia of motion.
\n4. Linear momentum = mass \u00d7 acceleration.
\n5. Two equal force acting in opposite directions are called unlike parallel forces.
\n6. If the resultant force of three force acting on body is zero then the forces are called balanced forces.
\n7. Torque is a scalar quantity.
\n8. Moment of couple = Force \u00d7 \u22a5r distance between line of action of forces
\n9. Principle of moments states that moment in clockwise direction = Moment in anti clockwise direction.
\n10. 1 Newton = 1 g cm s-2<\/sup>
\n11. Impulse = Force
\n12. Propulsion of rockets is based Newton’s third law of motion and conservation of linear momentum.
\n13. The value of universal gravitational constant is 6.674 \u00d7 10-11<\/sup> Nm\u00b2 kg-2<\/sup>
\n14. The relation between g and G is g = \\(\\frac{Gm}{R^2}\\)
\n15. The value of acceleration due to gravity decreases as the altitude of the body increases.
\n16. In a ‘free fall’ motion acceleration of the body is equal to the acceleration due to gravity.
\nAnswer:
\n1. True
\n2. False – If a motion does not depend on force then it is called as natural motion.
\n3. True
\n4. False – Linear momentum = mass \u00d7 velocity
\n5. True
\n6. True
\n7. False – Torque is a vector quantity
\n8. True
\n9. True
\n10. False – 1 Newton = 1 kg ms-2<\/sup>
\n11. False – Impulse = Change in momentum
\n12. True
\n13. True
\n14. False – The relation between g and G is g = \\(\\frac{GM}{R^2}\\)
\n15. True
\n16. True<\/p>\n<\/p>\n
IV. Match the following.<\/span><\/p>\nQuestion 1.
\nMatch the column A with column B.
\n
\nAnswer:
\nA. (iv)
\nB. (i)
\nC. (iii)
\nD. (v)
\nE. (ii)<\/p>\n
Question 2.
\nMatch the column A with column B.
\n
\nAnswer:
\nA. (iv)
\nB. (v)
\nC. (ii)
\nD. (i)
\nE. (iii)<\/p>\n
Question 3.
\nMatch the column A with column B.
\n
\nAnswer:
\nA. (ii)
\nB. (iv)
\nC. (v)
\nD. (i)
\nE. (iii)<\/p>\n
Question 4.
\nMatch the column A with column B.
\n
\nAnswer:
\nA. (iv)
\nB. (v)
\nC. (i)
\nD. (ii)<\/p>\n
V. Assertion and Reasoning.<\/span><\/p>\nQuestion 1.
\nAssertion: While travelling in a motor car we tend to remain at rest with respect to the seat.
\nReason: While travelling in a motor car we tend to move along the car with respect to the ground.
\n(a) Both Assertion and Reason are false.
\n(b) Assertion is true but Reason is false.
\n(c) Assertion is false but Reason is true.
\n(d) Both Assertion and Reason are true.
\nAnswer:
\n(d) Both Assertion and Reason are true.<\/p>\n
Question 2.
\nAssertion: When we kick a football it will roll over; when we kick a stone of the size of the football, it remains unmoved.
\nReason: Inertia of a body depends mainly on its mass.
\n(a) Both Assertion and Reason are true and Reason explains Assertion.
\n(b) Both Assertion and Reason are true but Reason doesn\u2019t explain Assertion.
\n(c) Both Assertion and Reason are false.
\n(d) Assertion is true but Reason is false.
\nAnswer:
\n(a) Both Assertion and Reason are true and Reason explains Assertion.<\/p>\n
<\/p>\n
Question 3.
\nAssertion: In a gun-bullet experiment, the acceleration of the gun is much lesser than the acceleration of the bullet.
\nReason: The gun has much smaller mass than the bullet.
\n(a) Both Assertion and Reason are false.
\n(b) Assertion is true but Reason is false.
\n(c) Assertion is false but Reason is true.
\n(d) Both Assertion and Reason are true.
\nAnswer:
\n(b) Assertion is true but Reason is false.<\/p>\n
Question 4.
\nAssertion: When a bullet is fired from a gun, the bullet moves forward, the gun moves backward.
\nReason: Total momentum before collision is equal to the total momentum .after collision.
\n(a) Both Assertion and Reason are true and Reason explains Assertion.
\n(b) Both Assertion and Reason are true but Reason doesn\u2019t explain Assertion.
\n(c) Assertion is true but Reason is false.
\n(d) Assertion is false but Reason is true.
\nAnswer:
\n(b) Both Assertion and Reason are true but Reason doesn\u2019t explain Assertion.<\/p>\n
Question 5.
\nAssertion: A person whose mass on earth is 125 kg will have his mass on moon as 250 kg.
\nReason: Mass varies from place to place.
\n(a) Both Assertion and Reason are true and Reason explains Assertion.
\n(b) Both Assertion and Reason are true but Reason doesn\u2019t explain Assertion.
\n(c) Both Assertion and Reason are false.
\n(d) Assertion is true but Reason is false.
\nAnswer:
\n(c) Both Assertion and Reason are false.<\/p>\n
Question 6.
\nAssertion: During turning a cyclist negotiates of the curve, while a man sitting in the car leans outwards of the curve.
\nReason: An acceleration is acting towards the centre of the curve.
\n(a) If both the assertion and the reason are true and the reason is the correct explanation of assertion.
\n(b) If both the assertion and the reason are true, but the reason is not the correct explanation of assertion.
\n(c) Assertion is true, but the reason is false.
\n(d) Assertion is false, but the reason is true.
\nAnswer:
\n(c) Assertion is true, but the reason is false.<\/p>\n
Question 7.
\nAssertion: On a rainy day, it is difficult to drive a car at high speed.
\nReason: The valve of coefficient of friction is lowered due to polishing of the surface.
\n(a) If both the assertion and the reason are true and the reason is the correct explanation of assertion.
\n(b) If both the assertion and the reason are true, but the reason is not the correct explanation of assertion.
\n(c) Assertion is true, but the reason is false.
\n(d) Assertion is false, but the reason is true.
\nAnswer:
\n(a) If both the assertion and the reason are true and the reason is the correct explanation of assertion.<\/p>\n
Question 8.
\nAssertion: A rocket moves forward by pushing the air backwards.
\nReason: It derives the necessary thrust to move forwarded according to Newton’s third law of motion.
\n(a) If both the assertion and the reason are true and the reason is the correct explanation of assertion.
\n(b) If both the assertion and the reason are true, but the reason is not the correct explanation of assertion.
\n(c) Assertion is true, but the reason is false.
\n(d) Assertion is false, but the reason is true.
\nAnswer:
\n(a) If both the assertion and the reason are true and the reason is the correct explanation of assertion.<\/p>\n
Question 9.
\nAssertion: A mass in the elevator which is falling freely, does not experience gravity.
\nReason: Inertial and gravitational masses have equivalence.
\n(a) If both the assertion and the reason are true and the reason is the correct explanation of assertion.
\n(b) If both the assertion and the reason are true, but the reason is not the correct explanation of assertion.
\n(c) Assertion is true, but the reason is false.
\n(d) Assertion is false, but the reason is true.
\nAnswer:
\n(c) Assertion is true, but the reason is false.<\/p>\n
Question 10.
\nAssertion: The intensity of gravitational field varies with respect to height and depth of a body on the Earth.
\nReason: The value of gravitational field intensity depends on height and depth of a body.
\n(a) If both the assertion and the reason are true and the reason is the correct explanation of assertion.
\n(b) If both the assertion and the reason are true, but the reason is not the correct explanation of assertion.
\n(c) Assertion is true, but the reason is false.
\n(d) Assertion is false, but the reason is true.
\nAnswer:
\n(d) Assertion is false, but the reason is true.<\/p>\n
<\/p>\n
VI. Answer briefly.<\/span><\/p>\nQuestion 1.
\nWhat is meant by mechanics? How can it be classified?
\nAnswer:
\nMechanics is the branch of physics that deals with the effect of force on bodies. It is divided into two branches namely statics and dynamics.<\/p>\n
Question 2.
\nWhat is statics?
\nAnswer:
\nStatics deals with the bodies, which are at rest under the action of forces.<\/p>\n
Question 3.
\nWhat is dynamics?
\nAnswer:
\nDynamics is the study of moving bodies under the action of forces.<\/p>\n
Question 4.
\nWhat is Kinematics?
\nAnswer:
\nKinematics deals with the motion of bodies without considering the cause of motion.<\/p>\n
Question 5.
\nWhat is Kinetics?
\nAnswer:
\nKinetics deals with the motion of bodies considering the cause of motion.<\/p>\n
Question 6.
\nDefine momentum. State its unit.
\nAnswer:
\nThe product of mass and velocity of a moving body gives the magnitude of linear momentum. It acts in the direction of the velocity of the object.
\nIts S.I unit is kg ms-1<\/sup>.<\/p>\nQuestion 7.
\nWhat is meant by a force?
\nAnswer:
\nForce is one that changes or tends to change the state of rest or of uniform motion of a body.<\/p>\n
Question 8.
\nState the effects of force.
\nAnswer:<\/p>\n
\n- Produces or tries to produce the motion of a static body.<\/li>\n
- Stops or tries to stop a moving body.<\/li>\n
- Changes or tries to change the direction of motion of a moving body.<\/li>\n<\/ol>\n
Question 9.
\nWhat is resultant force?
\nAnswer:
\nWhen several forces act simultaneously on the same body, then the combined effect of the multiple forces can be represented by a single force, which is termed as \u2018resultant force\u2019.<\/p>\n
Question 10.
\nWhat are balanced forces?
\nAnswer:
\nIf the resultant force of all the forces acting on a body is equal to zero, then the body will be in equilibrium. Such forces are called balanced forces.<\/p>\n
<\/p>\n
Question 11.
\nWhat are unbalanced forces?
\nAnswer:
\nForces acting on an object which tend to change the state of rest or of uniform motion of it are called unbalanced forces.<\/p>\n
Question 12.
\nWhat is meant by equilibriant?
\nAnswer:
\nA system can be brought to equilibrium by applying another force, which is equal to the resultant force in magnitude, but opposite in direction. Such force is called as \u2018Equilibriant\u2019.<\/p>\n
Question 13.
\nWhat is meant by couple? State few examples.
\nAnswer:
\nTwo equal and unlike parallel forces applied simultaneously at two distinct points constitute a couple. The line of action of the two forces does not coincide.
\nEg: Turning a tap, winding or unwinding a screw, spinning of a top, etc.<\/p>\n
Question 14.
\nA sudden application of brakes may cause injury to passengers in a car by collision with panels in front?
\nAnswer:
\nWith the application of brakes, the car slows down but our body tends to continue in the same state of motion because of inertia.<\/p>\n
Question 15.
\nWhen we are standing in a bus which begins to move suddenly, we tend to fall backwards. Why?
\nAnswer:
\nThis is because a sudden start of the bus brings motion to the bus as well as to our feet in contact with the floor of the bus. But the rest of our body opposes this motion because of its inertia.<\/p>\n
Question 16.
\nWhile travelling through a curved path, passengers in a bus tend to get thrown to one side. Justify.
\nAnswer:
\nWhen an unbalanced force is applied by the engine to change the direction of motion of the bus, passengers move to one side of the seat due to inertia of their body.<\/p>\n
Question 17.
\nDefine momentum of an object.
\nAnswer:
\nThe momentum of an object is defined as the product of its mass and velocity.<\/p>\n
Question 18.
\nDefine One newton.
\nAnswer:
\nThe amount of force required for a body of mass 1 kg produces an acceleration of 1 ms-2<\/sup>, 1 N = 1 kg ms-2<\/sup>.<\/p>\nQuestion 19.
\nDefine one dyne.
\nAnswer:
\nThe amount of force required for a body of mass 1 gram produces an acceleration of 1 cm s-2<\/sup>, 1 dyne = 1 g cm s-2<\/sup>; also
\n1 N = 105<\/sup> dyne.<\/p>\nQuestion 20.
\nWhat is unit force?
\nAnswer:
\nThe amount of force required to produce an acceleration of 1 ms-2<\/sup> in a body of mass 1 kg is called \u2018unit force\u2019.<\/p>\n<\/p>\n
Question 21.
\nWhat are the values of 1 kg f and 1 g f.
\nAnswer:
\n1 kg f= 1 kg \u00d7 9.8 m s-2<\/sup> = 9.8 N;
\n1 g f = 1 g \u00d7 980 cm s-2<\/sup> = 980 dyne<\/p>\nQuestion 22.