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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

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Class 9 Physics Chapter 4 Notes

Download Chapter 4 Notes

Class 9 Physics Chapter 4 SLO Notes

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Class 9 Physics Chapter 4 Notes SLO Notes

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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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

Net force


7 Component of vector acting along the x-axis,
(a) Horizontal component
(b) Vertical component
(c) x-component
(d) All of these
Show Answer

Horizontal component


8 Component of vector acting along the y-axis,
(a) Horizontal component
(b) Vertical component
(c) y-component
(d) All of these
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

25 N


21 The direction of resultant force is determined using which trigonometric function?
(a) Sine
(b) Cosine
(c) Tangent
(d) Secant
Show Answer

Tangent


22 The angle at which x and y components of force are equal is
(a) 0^°
(b) 30^°
(c) 45^°
(d) 60^°
Show Answer

45^°


23 Value of sin 45^° ,
(a) 0.56
(b) 0.707
(c) 0
(d) 1
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

Shape


27 The center of mass is generally represented by,
(a) CM
(b) CG
(c) MC
(d) GC
Show Answer

CM


28 The center of gravity is generally represented by,
(a) CM
(b) CG
(c) MC
(d) GC
Show Answer

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
Show Answer

Symmetry


30 The acceleration due to gravity ……………. with altitude.
(a) Stay same
(b) Increasing
(c) Decreases
(d) Zero
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

Torque


35 Torque is also known as,
(a) Moment of force
(b) Rotational motion
(c) Force
(d) None of these
Show Answer

Moment of force


36 Torque is a ……… quantity:
(a) Base
(b) Vector
(c) Scalar
(d) All of these
Show Answer

Vector


37 Torque is represented is by,
(a) \tau
(b) t
(c) M
(d) T
Show Answer

\tau


38 The mathematical formula for Torque is,
(a) \tau = F \times d
(b) \tau = ma
(c) \tau = mg
(d) None of these
Show Answer

\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
Show Answer

Nm


40 The rotation produced in a body depends upon ……….. factors
(a) 1
(b) 2
(c) 3
(d) 4
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

Moment arm


45 Moment arm is measured in,
(a) Kilogram
(b) Meter
(c) Second
(d) Newton
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

Static equilibrium


54 The study of objects in equilibrium is called,
(a) Statics
(b) Dynamic
(c) Kinetic
(d) All of these
Show Answer

Statics


Conditions of equilibrium

55 There are …………… conditions of equilibrium.
(a) 1
(b) 2
(c) 3
(d) 4
Show Answer

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
Show Answer

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
Show Answer

\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
Show Answer

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
Show Answer

\sum \tau =0


60 The symbol \sum used for,
(a) Summation
(b) Multiplication
(c) Division
(d) None of these
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

Unstable equilibrium


70 The total sum of forces acting on an object in static equilibrium is:
(a) Zero
(b) Unpredictable
(c) Constant
(d) Infinite
Show Answer

Zero


71 The total sum of torques acting on an object in rotational equilibrium is:
(a) Zero
(b) Negative
(c) Positive
(d) Variable
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

Neutral equilibrium


75 The weight of racing car is kept low to make it,
(a) Stable
(b) Unstable
(c) Strong
(d) None of these
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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
Show Answer

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


Dynamics

Dynamics


jawad khalil

jawad khalil

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