Class 9 Physics Chapter 4
Updated: 21 Oct 2023
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Class 9 Physics Chapter 4 is about “Turning Effect of Forces”. This article includes topics such as Force Diagrams, Like Parallel Forces, Unlike Parallel Forces, Head to Tail Rule, Addition of Forces, Resolution of Forces, Center of Mass, Center of Gravity, Rotational Motion, Rigid objects, Axis of Rotation, Difference between Center of Gravity and Center of Mass, Torque or Moment of Force, Clock and Anti-Clock wise Torque, Couple, Equilibrium, Conditions of equilibrium, First Condition of Equilibrium, Second Condition of Equilibrium, Principle of Moments, Types of Equilibrium, Static Equilibrium, Dynamic Equilibrium, Stability, Stable Equilibrium, Unstable Equilibrium and Neutral Equilibrium.
Class 9 Physics Chapter 4 Notes
Turning Effect of Forces Notes
Class 9 Physics Chapter 4 SLO Notes
Class 9 Physics Chapter 4 MCQs
Force Diagrams
1 Which of the following diagrams represents the forces acting on an object?(a) Force diagram
(b) Resultant diagram
(c) Motion diagram
(d) Velocity diagram
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Force diagram
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Like Parallel Forces
2 When two forces act in the same direction, they are called:(a) Like parallel forces
(b) Unlike parallel forces
(c) Anti-parallel forces
(d) All of these
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Like parallel forces
Unlike Parallel Forces
3 When two forces act in opposite directions, they are called:(a) Like parallel forces
(b) Unlike parallel forces
(c) Anti-parallel forces
(d) All of these
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Unlike parallel forces
Head to Tail Rule
4 The method of adding forces tip to tail is known as:(a) Like parallel forces
(b) Head to tail rule
(c) Force composition
(d) Resultant addition
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Head to tail rule
5 Addition of vectors are done by:
(a) Right hand rule
(b) Left hand rule
(c) Head to tail rule
(d) None of these
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Head to tail rule
Addition of Forces
6 The sum of all forces acting on an object is known as:(a) Balanced force
(b) Unbalanced force
(c) Net force
(d) Equilibrium force
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Net force
7 Component of vector acting along the x-axis,
(a) Horizontal component
(b) Vertical component
(c) x-component
(d) All of these
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Horizontal component
8 Component of vector acting along the y-axis,
(a) Horizontal component
(b) Vertical component
(c) y-component
(d) All of these
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Vertical component
9 The process of combining forces to get a single force, is
(a) Resolution of forces
(b) Subtraction of forces
(c) Addition of forces
(d) Multiplication of forces
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Addition of forces
10 When two forces act in the same direction, their magnitudes are 10N and 15N . What is the net force when added together,
(a) 5N
(b) 10N
(c) 15N
(d) 25N
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25N
11 When two forces act in the opposite direction, their magnitudes are same. What is the net force when added together?
(a) 0 N
(b) 10N
(c) 20 N
(d) 30 N
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0 N
12 A car is being pulled to the right with a force of 500 N and to the left with a force of 300 N. what is the net force acting on the car?
(a) 200 N to the right
(b) 200 N to the left
(c) 500 N to the right
(d) 500 N to the left
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200 N to the right
Resolution of Forces
13 The process of splitting a force vector into its component is,(a) Addition of forces
(b) Component of forces
(c) Resolution of forces
(d) None of these
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Resolution of forces
14 The process opposite to addition of forces is,
(a) Combination of forces
(b) Resolution of forces
(c) Net force
(d) All of these
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Resolution of forces
15 If the components of a force vector are perpendicular to each other then such components are called,
(a) Parallel components
(b) Perpendicular components
(c) Rectangular components
(d) Tangential component
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Rectangular components
16 The horizontal component of force vector F is represented by,
(a) F_x
(b) F_y
(c) F_z
(d) None of these
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F_x
17 The vertical component of force vector F is represented by,
(a) F_x
(b) F_y
(c) F_z
(d) None of these
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F_y
18 When resolving a force into components, the magnitudes of components are determined using which trigonometric functions?
(a) Sine and cosine
(b) Tangent and secant
(c) Sine and tangent
(d) Cosine and tangent
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Sine and cosine
19 A force of 50 N makes an angle of 30 \ degrees with the horizontal axis. What is the magnitude of horizontal component?
(a) 25 N
(b) 30 N
(c) 43.3 N
(d) 48.5 N
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43.3 N
20 A force of 50 N makes an angle of 30 degrees with the horizontal axis. What is the magnitude of vertical component?
(a) 25 N
(b) 30 N
(c) 43.3 N
(d) 48.5 N
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25 N
21 The direction of resultant force is determined using which trigonometric function?
(a) Sine
(b) Cosine
(c) Tangent
(d) Secant
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Tangent
22 The angle at which x and y components of force are equal is
(a) 0^°
(b) 30^°
(c) 45^°
(d) 60^°
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45^°
23 Value of sin 45^° ,
(a) 0.56
(b) 0.707
(c) 0
(d) 1
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0.707
Center of Mass
Center of Gravity
24 The point of a body about which the mass is equally distributed in all direction, is(a) Canter of mass
(b) Center of gravity
(c) Axis of rotation
(d) All of these
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Canter of mass
25 The point where whole weight of a body appear to act is called,
(a) Canter of mass
(b) Center of gravity
(c) Axis of rotation
(d) All of these
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Center of gravity
26 The position of center of gravity depends on ………… of a body.
(a) Size
(b) Weight
(c) Shape
(d) All of these
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Shape
27 The center of mass is generally represented by,
(a) CM
(b) CG
(c) MC
(d) GC
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CM
28 The center of gravity is generally represented by,
(a) CM
(b) CG
(c) MC
(d) GC
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CG
29 The center of gravity of a regular shaped body is always on its center of,
(a) Body
(b) Axis
(c) Symmetry
(d) None of these
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Symmetry
30 The acceleration due to gravity ……………. with altitude.
(a) Stay same
(b) Increasing
(c) Decreases
(d) Zero
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Decreases
Rotational Motion
31 The motion of a body about a fix point is said to be,(a) Circular motion
(b) Vibrational motion
(c) Rotational motion
(d) None of these
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Rotational motion
Rigid objects
32 The objects that do not deforms when move, are known as(a) Solid objects
(b) Rigid objects
(c) Strong objects
(d) None of these
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Rigid objects
Torque
Moment of Force
33 The rotational effect of a body is measured by a quantity known as:(a) Acceleration
(b) Velocity
(c) Displacement
(d) Torque
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Torque
34 Turning effect produced in a body about fixed point due to applied force is known as,
(a) Acceleration
(b) Torque
(c) Displacement
(d) Velocity
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Torque
35 Torque is also known as,
(a) Moment of force
(b) Rotational motion
(c) Force
(d) None of these
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Moment of force
36 Torque is a ……… quantity:
(a) Base
(b) Vector
(c) Scalar
(d) All of these
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Vector
37 Torque is represented is by,
(a) \tau
(b) t
(c) M
(d) T
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\tau
38 The mathematical formula for Torque is,
(a) \tau = F \times d
(b) \tau = ma
(c) \tau = mg
(d) None of these
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\tau = F \times d
39 The Moment of force is measured in,
(a) Kg/m^3
(b) Nm
(c) N/m
(d) N/m^2
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Nm
40 The rotation produced in a body depends upon ……….. factors
(a) 1
(b) 2
(c) 3
(d) 4
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2
41 If the rotation is produced in anti-clock wise direction then the torque is taken as:
(a) Opposite
(b) Perpendicular
(c) Positive
(d) Negative
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Positive
42 If the rotation is produced in clock wise direction then the torque is taken as:
(a) Opposite
(b) Perpendicular
(c) Positive
(d) Negative
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Negative
43 The point around which a rigid object rotates is called:
(a) Axis of rotation
(b) Center of mass
(c) Rotational pivot
(d) Fixed point
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Axis of rotation
44 The perpendicular distance between the axis of rotation and the line of action of the force is called:
(a) Moment arm
(b) Force distance
(c) Torque arm
(d) Radial arm
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Moment arm
45 Moment arm is measured in,
(a) Kilogram
(b) Meter
(c) Second
(d) Newton
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Meter
46 The force that causes an object to rotate about an axis is known as:
(a) Torque
(b) Moment arm
(c) Rotational force
(d) Centripetal force
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Centripetal force
Clock wise Torque
47 When a force tends to cause clockwise rotation, it is called:(a) Anti-clockwise torque
(b) Clockwise torque
(c) Rotational counterforce
(d) Inverse rotational force
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Clockwise torque
Anti-clock wise Torque
48 When a force tends to cause anti-clockwise rotation, it is called:(a) Anti-clockwise torque
(b) Clockwise torque
(c) Rotational counterforce
(d) Inverse rotational force
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Anti-clockwise torque
Couple
49 When two equal, opposite and parallel forces act at two points of the same body, they form a:(a) Torque
(b) Moment arm
(c) Force
(d) Couple
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Couple
50 What is the name given to two parallel forces with the same magnitude but opposite directions?
(a) Parallel forces
(b) Disparate forces
(c) Balanced forces
(d) Couple forces
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Couple forces
51 The distance between the two forces in a couple is known as:
(a) Torque distance
(b) Couple arm
(c) Moment arm
(d) Rotational distance
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Couple arm
52 A ……………. is always acting while opening or closing water tap, a lock, stopper of a bottle or jar:
(a) Couple
(b) Weight
(c) Force
(d) All of these
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Couple
Equilibrium
53 When an object is at rest and the sum of all forces acting on it is zero, it is known as:(a) Dynamic equilibrium
(b) Static equilibrium
(c) Translational equilibrium
(d) Rotational equilibrium
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Static equilibrium
54 The study of objects in equilibrium is called,
(a) Statics
(b) Dynamic
(c) Kinetic
(d) All of these
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Statics
Conditions of equilibrium
55 There are …………… conditions of equilibrium.(a) 1
(b) 2
(c) 3
(d) 4
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2
First Condition of Equilibrium
56 The first condition of equilibrium states that an object will remain at rest if:(a) The net force is zero
(b) The net torque is zero
(c) The net displacement is zero
(d) The net velocity is zero
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The net force is zero
57 The first condition of equilibrium is represented by,
(a) \sum F = 0
(b) \sum P = 0
(c) \sum \tau =0
(d) All of these
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\sum F = 0
Second Condition of Equilibrium
58 The second condition of equilibrium states that an object will remain in equilibrium if:(a) The net force is zero
(b) The net torque is zero
(c) The net displacement is zero
(d) The net velocity is zero
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The net torque is zero
59 The second condition of equilibrium is represented by,
(a) \sum F = 0
(b) \sum P = 0
(c) \sum \tau =0
(d) All of these
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\sum \tau =0
60 The symbol \sum used for,
(a) Summation
(b) Multiplication
(c) Division
(d) None of these
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Summation
Principle of Moments
61 The principle that states that for an object to be in equilibrium, the sum of clockwise torques must equal the sum of anticlockwise torques is called:(a) Equilibrium principle
(b) Principle of Moment
(c) Force balance principle
(d) Torque equilibrium principle
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Principle of Moment
Types of Equilibrium
Static Equilibrium
Dynamic Equilibrium
62 When an object is in motion with constant velocity, it is said to be in:(a) Static equilibrium
(b) Dynamic equilibrium
(c) Stable equilibrium
(d) Unstable equilibrium
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Dynamic equilibrium
63 When an object is in motion with uniform linear velocity, it is said to be in:
(a) Static equilibrium
(b) Dynamic translational equilibrium
(c) Dynamic rotational equilibrium
(d) Unstable equilibrium
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Dynamic translational equilibrium
64 When an object is in motion with uniform angular velocity, it is said to be in:
(a) Static equilibrium
(b) Dynamic translational equilibrium
(c) Dynamic rotational equilibrium
(d) Unstable equilibrium
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Dynamic rotational equilibrium
65 Paratrooper falling down with constant linear velocity is an example of,
(a) Static equilibrium
(b) Dynamic translational equilibrium
(c) Dynamic rotational equilibrium
(d) Unstable equilibrium
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Dynamic translational equilibrium
66 A compact disk (CD) rotating with constant angular velocity is an example of,
(a) Static equilibrium
(b) Dynamic translational equilibrium
(c) Dynamic rotational equilibrium
(d) Unstable equilibrium
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Dynamic rotational equilibrium
Stability
67 …………………. is a measure of how hard it is to displace an object from equilibrium.(a) Stability
(b) Force
(c) Torque
(d) Equilibrium
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Stability
Stable Equilibrium
Unstable Equilibrium
Neutral Equilibrium
68 An equilibrium position where a small displacement from the position cause a restoring force is called:(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Stable equilibrium
69 An equilibrium position where a small displacement from the position results in an increased displacement is called:
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Unstable equilibrium
70 The total sum of forces acting on an object in static equilibrium is:
(a) Zero
(b) Unpredictable
(c) Constant
(d) Infinite
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Zero
71 The total sum of torques acting on an object in rotational equilibrium is:
(a) Zero
(b) Negative
(c) Positive
(d) Variable
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Zero
72 In which state of equilibrium the center of gravity raised than the original position.
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Stable equilibrium
73 In which state of equilibrium the center of gravity lowered than the original position.
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Unstable equilibrium
74 In which state of equilibrium the center of gravity remain same as the original position.
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Neutral equilibrium
75 The weight of racing car is kept low to make it,
(a) Stable
(b) Unstable
(c) Strong
(d) None of these
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Stable
76 A physics book lying on the table is an example of ……………..
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Stable equilibrium
77 A ball balanced on the tip of narrow cone is an example of……….
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Unstable equilibrium
78 Motion of rolling ball on ground is an example of ………………..
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) Dynamic equilibrium
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Neutral equilibrium
79 The stability of a body can be increased by …………….. the area of support.
(a) Increasing
(b) Decreasing
(c) Keeping the same
(d) All of these
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Increasing
80 The stability of a body can be increased by …………….. the center of mass.
(a) Raising
(b) Lowering
(c) Accelerating
(d) None of these
Show Answer
Lowering
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