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##### Question: 1

Unit of torque.

##### Answer: 1

1-123It unit newton metre.

##### Question: 2

Define centre of mass

##### Answer: 2

2-123Centre of mass of a system is a point where an applied force causes the system to move without rotation.

##### Question: 3

Differentiate between like and unlike forces.

##### Answer: 3

3-123Like parallel forces:
such a parallel forces whoe direction is same are called like parallel force.
Example: the weights of apples in a sack are parallel to each other and also in the same direction.

##### Question: 4

What is 2nd condition for equilibrium?

##### Answer: 4

4-123A body is said to be satisfy 2nd condition of equilibrium if the resultant torque acting on a body is zero.

##### Question: 5

Differentiate between torque and couple.

##### Answer: 5

5-123Torque is produced by only only force
one moment arm is there to produce the torque

##### Question: 6

What is centre of gravity.

##### Answer: 6

6-123A point where the whole weight of the body appears to act vertically downward is called centre of gravity of a body e.g. centre of gravity of uniform rod is centre of the rod.

##### Question: 7

Define parallel forces.

##### Answer: 7

7-123When a number of forces acting on a body in such a way that their point of action s are different but line of action are parallel to each other ,are called parallel forces.

##### Question: 8

When a body is said to be in equilibrium?

##### Answer: 8

8-123A body is said to be in equilibrium if no net force acts on it.

##### Question: 9

Give an example of a moving body which is in equilibrium.

##### Answer: 9

9-123WA paratrooper coming down with the constant speed is in equilibrium as well as in motion.

##### Question: 10

Explain 1st condition of equilibrium.

##### Answer: 10

10-123A body said to satisfy first condition of equilibrium if the resultant of all these forces acting on it is zero.

##### Question: 11

Define unlike parallel forces.

##### Answer: 11

11-123Such parallel forces which are opposite in direction are called unlike parallel forces.

##### Question: 12

Define Resultant vector.

##### Answer: 12

12-123A resultant vector is a single vector that has the same effect as the combined effect of all vectors to be added.

##### Question: 13

Define Trigonometry.

##### Answer: 13

13-123The branch of geometry which explains the properties of right angle triangle is called trigonometry.

##### Question: 14

Write the types of parallel force.

##### Answer: 14

14-123i) Like parallel forces.
ii) Unlike parallel forces.

##### Question: 15

Define equilibrium. and give one example.

##### Answer: 15

15-123A body is said to be in equilibrium, if no net force acts on it.
Example: i) A book lying on a table is in equilibrium because the weight of book and force of reaction of table are in opposite direction and hence cancel their effect.

##### Question: 16

Define unstable equilibrium. Give one example

##### Answer: 16

16-123Unstable equilibrium: If a body does not return to its previous position when set free after a slightest is said to be in unstable equilibrium.
Example: A pencil just balanced at its tip with centre of gravity at the highest position is the example of unstable equilibrium=brium

##### Question: 17

What is meant by resolution of forces?

##### Answer: 17

17-123The decomposition or division of a vector into itscomponent is called resolution of a vector or force

##### Question: 18

What is line of action of force.

##### Answer: 18

18-123A line along which a force acts is called line of action of the force.

##### Question: 19

Define Trigonometric ratio.

##### Answer: 19

19-123The ratios between any two sides of a right angle triangle are called trigonometric ratio.

##### Question: 20

What is meant by principle of moments?

##### Answer: 20

20-123A body is balanced if the sum of clockwise moments acting on the body is equal to the sum of anticlockwise moments acting on its.

##### Question: 21

Give an example of a moving body which is in equilibrium?

##### Answer: 21

21-123A paratroopercoming down with terminal velocity is in equilibrium this type of equilibrium.

##### Question: 22

Define couple arm.

##### Answer: 22

22-123The perpendicular distance between two forces of couple is called couple arm.

##### Question: 23

Difference between like and unlike forces?

##### Answer: 23

23-123Like forces:like forces are the forces that are parallel to each other and have the same direction

##### Question: 24

Define moment arm.

##### Answer: 24

24-123The perpendicular distance between the axis of rotation and line of action of force is called moment arm.

##### Question: 25

Define parallel forces and types?

##### Answer: 25

25-123In a plane, if number of forcesact on a body such that their points of action are different, but lines of action are parallel to each other, then these forces are called parallel forces.

There are two types of parallel forces

1- like parallel forces, unlike parallel forces

##### Question: 26

How head to tail rule helps to find the resultant of forces

##### Answer: 26

26-123When two forces are added with head to tail rule it gives the resultant of two forces, It gives the magnitude and direction both of the resultant force.

##### Question: 27

Which factor torque depends.

##### Answer: 27

27-123Torque = F X L
So, Torque depends upon force and moment arm.

##### Question: 28

What is centre of gravity

##### Answer: 28

28-123Centre of Gravity: A point where whole weight of the body appears to act vertically downward is called centre of gravity of a body e.g centre of gravity of uniform rod is centre of the rod

##### Question: 29

Define Resolution of vectors.

##### Answer: 29

29-123Resolution of Vectors: to split up a force into its perpendicular components is called resolution of forces.

##### Question: 30

Define first condition of equilibrium?

##### Answer: 30

30-123A body will be in equilibrium if the resultant of all the forces acting on it is zero this is first condition of equilibrium.

##### Question: 31

Define like parallel forces.

##### Answer: 31

31-123Such parallel forces which have same direction are called like parallel forces.

##### Question: 32

When a body is said to be in equilibrium

##### Answer: 32

32-123A body is said to be in equilibrium if no net force acts on it.

##### Question: 33

Define axis of rotation.

##### Answer: 33

33-123The line about which a body rotates is called axis of rotation.

##### Question: 34

Difference between Center of mass and center gravity?

##### Answer: 34

34-123Center of mass.

Center of mass of a system is such a point where an applied force cause the system to move without rotation

##### Question: 35

Differentiate between like and unlike forces

##### Answer: 35

35-123Like Parallel forces: Such a parallel forces whose direction is same called are called like parallel forces

Example: The weights of apples in a sack are parallet to each other and also in the same direction.

##### Question: 36

Define couple with the help of an example.

##### Answer: 36

36-123Couple: A couple is formed by two unlike parallel forces same magnitude but not along the same line.

##### Question: 37

Why the height of a vehicle is kept as low as possible

##### Answer: 37

37-123To lower the centre of mass of vehicles their height is kept low. Low centre of mass make them more stable as compare to the high centre of mass Due to this vehicles are made heavy at the bottom and their height is kept minimum

##### Question: 38

What is meant by additionof forces?

##### Answer: 38

38-123Force is a vector quantity. It has magnitude as well direction; therefore forces are not added by ordinaryarithmetic rules. They are added by a method known as head to tail rule .

##### Question: 39

What is stat of neutral equilibrium.

##### Answer: 39

39-123Neutral Equilibrium; If a body remains in its new position when disturbed from its previous position, then body is said to be in neutral equilibrium.

##### Question: 40

Two children are sitting on the sea-saw such that they cannot swing

##### Answer: 40

40-123In this situation the net torque is zero

##### Question: 41

Why the height of vehicles is kept as low as possible?

##### Answer: 41

41-123We Know that smaller the height of center of gravity of a body , greater will be its stability . The height of vehicles is kept low to lower their center of gravity and as a result their stability increases.

##### Question: 42

Define stable equilibrium with example.

##### Answer: 42

42-123Stable equilibrium: A body is said to be in stable equilibrium if after a slightest it returns to its previous position.
Example: If a book returns to its previous position after a slightest tilt then book is said be in stable equilibrium.

##### Question: 43

What is 2nd condition for equilibrium

##### Answer: 43

43-123A body is said to be satisfy 2nd condition of equilibrium if the resultant torque acting on a body is zero

##### Question: 44

Define plumb line?

##### Answer: 44

44-123A plum be line is a piece of string with a weight attached to the end that is used to check that something such as wall is vertical

##### Question: 45

In a right angled triangle length of base is 4cm and its perpendicular is 3cm.

##### Answer: 45

45-123length of its hypotenuse, cos , sin, tan,

##### Question: 46

Define rigid body and give an example.

##### Answer: 46

46-123Rigid body is composed of large number of particles. If the distance between all pairs of particles of the body do not change by applying a force, then it is called a rigid body.
Example: Adoor , a cylinder.

##### Question: 47

Can force be added by ordinary addition of number

##### Answer: 47

47-123No, forces cannot be added by ordinary addition of number They can be added by head to tail rule because force is vector quantity

##### Question: 48

Differentiate between stable and neutral equilibrium.

##### Answer: 48

48-123Stable equilibrium: A body is said to be in stable equilibrium if after a slight tilt it returns to its previous position

In stable equilibrium centre of gravity of the body is at its lowest position and after the slight tilt it return to its previous position.

##### Question: 49

Define Resultant vector?

##### Answer: 49

49-123A resultant vector is a single force that has the same effect as the combined effect of all the forces to be added.

##### Question: 50

Define trigonometry

##### Answer: 50

50-123The branch of geometry which explains the properties of right angle triangle is called trigonometry.

##### Question: 51

Define couple and couple arm?

##### Answer: 51

51-123A couple is formed by two unlike parallel forces of the same magnitude, but not along the same line

##### Question: 52

A ladder leaning at a wall as shown in figure is in equilibrium how

##### Answer: 52

52-123The weight of ladder produces anticlock wise torque. The wall pushes the ladder at its tope end thus produce a clockwise torque. Both torques are equal and opposite and cancel their effect. So, the ladder is in state of equilibrium.

##### Question: 53

Define Resultant Vector

##### Answer: 53

53-123A resultant vector is a single vector that has the same effect as the combined effect of all vector to be added

##### Question: 54

Head to tale rule explain?

##### Answer: 54

54-123Draw the representative lines of all the vector to be added in such a way that head of first vector coincides with the tail of second vector, head of second vector coincides with the tail of third vector and on so

##### Question: 55

Explain 1st condition for equilibrium.

##### Answer: 55

55-123A body is said satisfy first condition of equilibrium if the resultant of all these forces acting on it is zero.

F=0

##### Question: 56

Give an example of a moving body which is in equilibrium

##### Answer: 56

56-123A paratrooper coming down with the constant speed is in equilibrium as well as in motion

##### Question: 57

Does the fan satisfy second condition for equilibrium when rotating with uniform speed

##### Answer: 57

57-123Yes, It satisfy because moment arm is zero than

##### Question: 58

What is line of action force

##### Answer: 58

58-123A line along which a force acts is called line of action of the force

##### Question: 59

What is head to tail rule

##### Answer: 59

59-123When two or more than two vectors are added such that the head of the first vector is joined with tail of second vector and finally the tail of first vector is joined with the head of the second vector. This method of addition is called head to tail rule. The vector joining the tail of first vector to the head of last vector is called resultant vector a Graphical method used to find the resultant of two or more forces is called head to tail rule.

##### Question: 60

How a force can be resolved into its prependicular components

##### Answer: 60

60-123To resolve a force into its perpendicular components we neend head to tail rule. It the given forces is considered as resultant force then the two components can be drawn In the figure force F is making an angle 0 with horizontal surface and it is resolved into Fx and Fy which are horizontal and vertical components respectively.

##### Question: 61

Define torque

##### Answer: 61

61-123Turning effect of a force is called torque or moment of force

##### Question: 62

Why a body regain its previous state in stable equilibrium

##### Answer: 62

62-123Because in stable equilibrium its centre of gravity is at the lowest position

##### Question: 63

Why door is easy to open or close by pushing or pulling at handle?

##### Answer: 63

63-123We open or close a door by pushing it . Here push or pull turn the door about its hinge or axis of rotation, The door is opened or closed due to the turning effect of the force acting on it.

##### Question: 64

Why there is need for 2nd condition of equilibrium if body satisfy 1st condition of equilibrium

##### Answer: 64

64-123If a body satisfied 1st condition of equilibrium then it is not completely in equilibrium. Because there is a chance of producing torque in that body

If two same force are acting on a body in opposite direction in a same line then no rotation is produced but if those two forces act in different lines then the torque is produced so we need another condition for equilibrium to eliminate the torques.

##### Question: 65

What is base

##### Answer: 65

65-123The smaller side of right angle triangle with angle is called base e,g the side AB in the figure is base.

##### Question: 66

The weight of the ladder in fig produces an anticlock wise toruqe

##### Answer: 66

66-123Yes, the ladder is in state of equilibrium.

##### Question: 67

Define parallel forces

##### Answer: 67

67-123When a number of forces acting on a body in such a way that their point of actions are different but lines of action are parallel to each other are called parallel forces.

##### Question: 68

Can a small child play with a fat child on the sea-saw Explain how

##### Answer: 68

68-123Yes a small child can play with a fat child if the fat child sists near the axis of rotation of the sea-saw and the small child sists away the axist of rotation.

##### Question: 69

Think of a body which is at test but not in equilibrium

##### Answer: 69

69-123When we throw a body in up ward direction at its highest position the body is at rest for a moment but it is not in equilibrium because no other force is present to cancel the force of weight.

##### Question: 70

Define equilibrium and give its example

##### Answer: 70

70-123Equilibrium: A body is said toi be in equilibrium if no net force acts on it

##### Question: 71

Define resolution of vectors

##### Answer: 71

71-123To split up a force into its perpendicular components is called resolution of forces.

##### Question: 72

Define couple arm

##### Answer: 72

72-123The perpendicular distance between two force of couple is called couple arm

##### Question: 73

Does the speed of a ceiling fan go on increasing all the time.

##### Answer: 73

73-123No, speed of a ceiling fan is not increasing all the time but it is constant.

##### Question: 74

What is state of neutral equilibrium

##### Answer: 74

74-123Neutral Equilibrium: If a body remains in its new position when disturbed from its previous position then body is said to be in neutral equilibrium

##### Question: 75

Why a body cannot be in equilibrium due to single force acting on it

##### Answer: 75

75-123When a single force acts on a body acceleration and torque is produced due to this reason a body is not equilibrium.

##### Question: 76

On which factor torque depends

##### Answer: 76

76-123So, torque depends upon force and moment arm

##### Question: 77

Discuss centre of gravity of some symmetrical object

##### Answer: 77

77-123Uniform rod, Square plate and rectangular plate, Uniform circular disc, Uniform solid sphere, Triangular plate, Uniform solid or hollow cylinder,

##### Question: 78

Define like parallel forces and moment arm

##### Answer: 78

78-123Like parallel forces: Like parallel force are the forces that are parallel to each other and have the same direction

##### Question: 79

What is perpendicular

##### Answer: 79

79-123The line facing the angle in a right angle triangle is called perpendicular e.g the side BC in the figure is perpendicular

The line have 90 angle with any plane is called perpendicular

##### Question: 80

Why the handle of a door is placed at the outer edge of the door

##### Answer: 80

80-123We can open or close door more easily by applying a force at the outer edge of a door rather than near the hinge (axist ) Because by this a long moment arm is obtained which produce more torque which helps to open the door more easily.

##### Question: 81

Write the types of parallel forces

##### Answer: 81

81-123There are two types of parallel forces.

Like parallel force

Unlike parallel force

##### Question: 82

What is meant by perpendicular components

##### Answer: 82

82-123Perpendicular Component: Those components which makes an angle of 90 with each other are called perpendicular components. The perpendicular components of force is fx and fy

##### Question: 83

Why a body cannot be in equilibrium due to a single force acting on it

##### Answer: 83

83-123A body cannot be in equilibrium due to a single force because a single force cannot be considered zero as a net force and the torque produced by it will also not be zero

##### Question: 84

What is directional graph

##### Answer: 84

84-123To draw a vector on a paper we need direction Graphically two mutually perpendicular lines are used to indicate the direction. These two line are used to direct a vector on paper or plane.

##### Question: 85

Differentiate between Axis of rotation and Mometn

##### Answer: 85

85-123Axis of rotation The straight line passing through a body about which the body can rotate is called axis of rotation

##### Question: 86

Define axis of rotation

##### Answer: 86

86-123The line about which a body rotates is called axis of rotation

##### Question: 87

What is hypotenuse

##### Answer: 87

87-123The facing the angle of 90 is called hypotenuse e.g the side AC in the figure is hypotenuse

In right angle triangle the side opposite to right angle is called hypotenuse

##### Question: 88

Define like parallel forces

##### Answer: 88

88-123Such parallel forces which have same direction are called like parallel forces. e.g in the above figure f1 and f2 are like parallel to each other and the weight of apples closed in a sack are also in downward direction. These forces are also parallel forces.

##### Question: 89

Define equilibrium

##### Answer: 89

89-123Equilibrium: A body is said to be in equilibrium if no net force acts on it. A body in equilibrium thus remains at rest or moves with uniform velcity

##### Question: 90

Define like and unlike parallel forces

##### Answer: 90

90-123Like parallel forces: Like parallel forces are the forces that are parallel to each other and have the same direction

##### Question: 91

What is right angle triangle

##### Answer: 91

91-123A triangle having an angle of 90 in it is called Right angle triangle.

##### Question: 92

What is meant by principle of moments

##### Answer: 92

92-123A body is balance if the sum of clockwise moments acting on the body is equal to the sum of anticlock wise moments acting on its

##### Question: 93

A force of 150 N is making an angle of 40 with horizontal surface what is its vertical components.

##### Answer: 93

93-123Given data: Give data F= 15N

0=40

##### Question: 94

Write the principle of moments

##### Answer: 94

94-123State the principle of moments: A body initially at rest does not rotate if the sum of all the clockwise moments acting on it balanced by the sum of all the anti clockwise moment acting on it This principle is known as the principle of moments. Mathematically clockwise moments=Anti-clockwise moments

##### Question: 95

Force of 150N can loosen a nut when applied at end of a spanner 10cm long

##### Answer: 95

95-123Given data: F=150N

L=10cm=01.m

##### Question: 96

How head to tail rule helps us to find resultant of vectors

##### Answer: 96

96-123To determine resultant vector by head to tail rule we have to draw the resultant vector from head of last to tail of 1st vector It given us resultant graphically

##### Question: 97

Define unstable equilibrium

##### Answer: 97

97-123Unstable Equilibrium: If a body does not return to its previous position when set free after a slightest tilt is said to be in unstable equilibrium

##### Question: 98

Why the height of vehicles is kept as low as possible

##### Answer: 98

98-123The height of vehicles is kept as low as possible to make them more and more stable because stability increased as height of vehicle decrease.

##### Question: 99

What is line of action of force

##### Answer: 99

99-123Line of action of force and moment arm always makes angle 90 with each other

##### Question: 100

What is Plumb line

##### Answer: 100

100-123Plumb line: A plumb line consists of a small metal bob lead or brass supported by a string. When the bob is suspended freely by the string, it rests the vertical direction due to its weight acting vertically down ward.

##### Question: 101

At which point an applied force does not produce rotation

##### Answer: 101

101-123A force applied at the centre of mass of a body does not produce any rotation rather the body moves in the direction of applied force

##### Question: 102

How can we increase the stability of a vehicle

##### Answer: 102

102-123Stability of the vehicle can be increased by lowering the centre of mass of vehicle and by making them heavy at the bottom.

##### Question: 103

Think of a body which is at rest but not in equilibrium

##### Answer: 103

103-123A body thrown vertically upward at maximum height is at rest for a while but at that moment gravitational force

##### Question: 104

Why a body does not regain its previous state in unstable equilibrium

##### Answer: 104

104-123Because in this state centre of gravity of body is at highest position.

##### Question: 105

Define Resolution of forces

##### Answer: 105

105-123Forces into their component forces is called resolution of forces

##### Question: 106

Explain couple with the help of an example

##### Answer: 106

106-123Couple A Couple is formed act on a steering wheel and produce torque to torque to turn the vehicle

##### Question: 107

Define resultant of forces and explain by diagram

##### Answer: 107

107-123Resultant of forces: A resultant force is a single force that has the same effect as the combined effect of all the force to be added

##### Question: 108

Where are the centre of gravity of uniform square and uniform triangular sheets.

##### Answer: 108

108-123Centre of gravity of a square of a rectangular Square: The centre of a gravity of a uniform square or a rectangular sheet is the point of intersection of its diagonals

##### Question: 109

Define center of gravity

##### Answer: 109

109-123Resultant vector: A resultant vector is a single vector that the same effect as the combined effect of all the vectors be added

##### Question: 110

Define rigid body and give an example

##### Answer: 110

110-123Rigid Body: A body is composed of large number of particles. It the distance between all pairs of particles of the body do not change by applying a force, then it is called a rigid body

##### Question: 111

Differentiate between clockwise and anti-clockwise moment

##### Answer: 111

111-123Clockwise Moment: The force that trrns a spanner in the clockwise direction is known is clockwise force. The torque or moment of force produced to this force is called clockwise moment

The moment produced during tighten a nut

##### Question: 112

Define parallel forces. Write n names of its types

##### Answer: 112

112-123Parallel forces: Such forces which are parallel to each other are called parallel forces.

##### Question: 113

Define Centre of mass of a body

##### Answer: 113

113-123Centre of mass: The point where when the force is applied, the system move without rotation is called centre of mass.

##### Question: 114

Define stable equilibrium with example

##### Answer: 114

114-123Stable Equilibrium: A body is said to be in stable equilibrium if after a slightest tilt it returns to its previous postion.

##### Question: 115

What is meant by graph

##### Answer: 115

115-123A graph is a diagram showing the relationship between variable quantities typically of two variables, each measured along a pair of axis at right angle.

##### Question: 116

What is difference between stable and unstable

##### Answer: 116

116-123Stable: equilibrium: A body is said to be in stable equilibrium if after a slight tilt it return to its previous position.

##### Question: 117

Define torque and Center of mass

##### Answer: 117

117-123Torque: The turning effect of a force is called torque or moment of the force

##### Question: 118

On doubling the moment arm, what will be its effect on the value of torque

##### Answer: 118

118-123On doubling the moment arm the value of torque will also be double

##### Question: 119

What is meant by Rigid body

##### Answer: 119

119-123Rigid Body: A body is composed of large number of small particles. If the distance between all pairs of particles of the body do not change by applying of force the, it is called rigid body A rigid body is the one that is not deformed by force or forces acting on it

##### Question: 120

What is meant by Couple of forces

##### Answer: 120

120-123Couple: A Couple is formed by two unlike parallel forces of the same magnitude but not along the same line.

##### Question: 121

Differentiate between torque and couple

##### Answer: 121

121-123Torque: Turing effect of force is called torque .

To produce a torque we need only one force at least

Torque or moment of force is equal to product of force F and moment arm L

##### Question: 122

What is the second condition of equilibrium

##### Answer: 122

122-123First condition of equilibrium: A body is said to satisfy first condition for equilibrium if the resultant of all the forces acting on it is zero,

Formula F=0

##### Question: 123

Why are vehicles made heavy at the bottom

##### Answer: 123

123-123Vehicles are made heavy at the bottom to lower their centre of gravity to keeps the balanced vehicles.