Class 9 Physics Chapter 2
Updated: 05 Dec 2024
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Class 9 Physics Chapter 2 is about “Kinematics”. This article includes topics such as Definition of Kinematics, Rest and Motion, Types of Motion, Rest and Motion are Relative, Scalar and Vector Quantities, Distance, Displacement, Speed and types of speed (Average Speed, Instantaneous Speed, Uniform and Variable Speed ), Velocity and types of Velocity (Average Velocity, Instantaneous Velocity, Uniform and Variable Velocity ), Acceleration and types of Acceleration (Average Acceleration, Instantaneous Acceleration, Uniform and Variable Acceleration ), Deceleration/Retardation, Distance-Time Graph, Speed-Time Graph, Velocity Time Graph, Equations of Motion( First Equation of Motion, Second Equation of Motion, Third Equation of Motion) and Motion due to Gravity.
Class 9 Physics Chapter 2 Notes
Kinematics Notes
Kinematics SLO Based Notes
Physics Class 9 Chapter 2-MCQs
Kinematics
(1). The branch of physics that deals with the study of motion, forces, and energy in physical systems is:(a) Thermodynamics
(b) Optics
(c) Mechanics
(d) Electricity
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Correct Option: (c) Mechanics
Explanation:
Mechanics is the branch of physics that deals with the study of motion, forces, and energy in physical systems.
(a) Kinematics
(b) Mechanics
(c) Dynamics
(d) Motion
Show Answer
Correct Option: (a) Kinematics
Explanation:
Kinematics is the branch of mechanics that deals with the study of motion without considering the forces causing the motion.
Rest and Motion
Rest
(3). When a body does not change its position with respect to some reference then it will be in the state of:(a) Rest
(b) Motion
(c) Rotatory motion
(d) Vibratory motion
Show Answer
Correct Option: (a) Rest
Explanation:
When a body does not change its position with respect to some reference point, it is said to be at rest.
Motion
(4). When a body changes its position with respect to some reference then it will be in the state of:(a) Rest
(b) Motion
(c) Rotatory motion
(d) Vibratory motion
Show Answer
Correct Option: (b) Motion
Explanation:
When a body changes its position with respect to some reference point, it is said to be in motion.
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Types of Motion
(5). Which type of motion refers to the change in position of a body as a whole?(a) Rotational motion
(b) Curvilinear motion
(c) Translatory motion
(d) Rectilinear motion
Show Answer
Correct Option: (c) Translatory motion
Explanation:
Translatory motion refers to the change in position of a body as a whole.
(a) Rotational motion
(b) Curvilinear motion
(c) Translatory motion
(d) Rectilinear motion
Show Answer
Correct Option: (d) Rectilinear motion
Explanation:
Rectilinear motion refers to the motion of an object along a straight line with no change in direction.
(a) Rotational motion
(b) Curvilinear motion
(c) Translatory motion
(d) Rectilinear motion
Show Answer
Correct Option: (b) Curvilinear motion
Explanation:
Curvilinear motion refers to the circular or curved path motion.
(a) Rotational motion
(b) Curvilinear motion
(c) Random motion
(d) Rectilinear motion
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Correct Option: (c) Random motion
Explanation:
Random motion refers to the irregular motion of a body.
(a) Rectilinear motion
(b) Curvilinear motion
(c) Rotational motion
(d) Random motion
Show Answer
Correct Option: (d) Random motion
Explanation:
The motion of gas molecules is an example of random motion.
(a) Curvilinear motion
(b) Translatory motion
(c) Rotational motion
(d) Vibrational motion
Show Answer
Correct Option: (c) Rotational motion
Explanation:
Rotational motion occurs when an object moves around a fixed axis or a point, such as the Earth’s rotation on its axis.
(a) Curvilinear motion
(b) Translatory motion
(c) Rotational motion
(d) Vibrational motion
Show Answer
Correct Option: (d) Vibrational motion
Explanation:
Vibrational motion involves back-and-forth oscillations around an equilibrium position.
(a) Curvilinear motion
(b) Translatory motion
(c) Rotational motion
(d) Vibrational motion
Show Answer
Correct Option: (d) Vibrational motion
Explanation:
The swinging of a pendulum or a child on a swing is an example of vibrational motion as it oscillates back and forth around a central equilibrium position.
Position
(13). …………….. is the location of an object relative to some reference?(a) Distance
(b) Length
(c) Position
(d) None of these
Show Answer
Correct Option: (c) Position
Explanation:
Position describes the location of an object relative to a reference point.
Rest and Motion are Relatives
(14). Rest and motion are …………. states.(a) Relative
(b) Absolute
(c) Constant
(d) All of these
Show Answer
Correct Option: (a) Relative
Explanation:
Rest and motion are relative states because they depend on the observer’s frame of reference.
For example, a person sitting in a moving car is at rest relative to the car but in motion relative to the road.
Scalar and Vector Quantities
(15). All those quantities which are completely specified by their magnitude only are said to be:(a) Scalars
(b) Vectors
(c) Speed
(d) Velocity
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Correct Option: (a) Scalars
Explanation:
Scalars are quantities that are specified by their magnitude only, without direction.
Examples:
mass, time, speed, and temperature.
(a) Scalars
(b) Vectors
(c) Speed
(d) Velocity
Show Answer
Correct Option: (b) Vectors
Explanation:
Vectors are quantities that are specified by both magnitude and direction. Examples of vectors include velocity, force, displacement, and acceleration.
(a) Velocity
(b) Time
(c) Displacement
(d) Acceleration
Show Answer
Correct Option: (b) Time
Explanation:
Time is a scalar quantity as it only has magnitude.
(a) Temperature
(b) Mass
(c) Time
(d) Displacement
Show Answer
Correct Option: (d) Displacement
Explanation:
Displacement is a vector quantity as it has both magnitude and direction.
(a) Scalar
(b) Vector
(c) Both (a) and (b)
(d) None of these
Show Answer
Correct Option: (b) Vector
Explanation:
Force is a vector quantity as it has both magnitude and direction.
(a) Scalar
(b) Vector
(c) Both (a) and (b)
(d) None of these
Show Answer
Correct Option: (a) Scalar
Explanation:
Time is a scalar quantity as it is specified by magnitude only.
Distance
(21). The length of a path traveled between two positions is called:(a) Velocity
(b) Acceleration
(c) Distance
(d) Retardation
Show Answer
Correct Option: (c) Distance
Explanation:
Distance is the total length of the path traveled by an object.
(a) Distance
(b) Displacement
(c) Velocity
(d) Acceleration
Show Answer
Correct Option: (a) Distance
Explanation:
Distance is a scalar quantity as it only has magnitude.
(a) Newton
(b) Meter
(c) Pascal
(d) Joule
Show Answer
Correct Option: (b) Meter
Explanation:
The meter (m) is the SI unit for measuring distance, representing the length of the path an object travels.
Displacement
(24). The shortest distance between two points is known as:(a) Distance
(b) Displacement
(c) Velocity
(d) Acceleration
Show Answer
Correct Option: (b) Displacement
Explanation:
Displacement is the shortest distance and it is a vector quantity.
(a) Scalar
(b) Vector
(c) Tensor
(d) None of these
Show Answer
Correct Option: (b) Vector
Explanation:
Displacement is a vector quantity as it has both magnitude and direction.
(a) Newton
(b) Meter
(c) Pascal
(d) Joule
Show Answer
Correct Option: (b) Meter
Explanation:
The unit of displacement is also the meter (m).
(a) Displacement = final position – initial position
(b) Displacement = speed × time
(c) Displacement = distance × time
(d) None of these
Show Answer
Correct Option: (a) Displacement = final position – initial position
Explanation:
Displacement is the change in position, which can be calculated as the final position minus the initial position.
For example, if an object moves from position 2 m to 8 m, its displacement is 8 – 2 = 6 m.
Speed
(28). The distance covered by a body in unit time is known as:(a) Velocity
(b) Speed
(c) Distance
(d) Displacement
Show Answer
Correct Option: (b) Speed
Explanation:
Speed is the distance covered by an object in a unit of time.
(a) Meters per second (m/s)
(b) Kilometers per hour (km/h)
(c) Meter
(d) Second
Show Answer
Correct Option: (a) Meters per second (m/s)
Explanation:
The SI unit of speed is meters per second.
For example, if an object moves 10 meters in 2 seconds, its speed is 10 m / 2 s = 5 m/s.
(a) Scalar
(b) Vector
(c) Tensor
(d) None of these
Show Answer
Correct Option: (a) Scalar
Explanation:
Speed is a scalar quantity as it only has magnitude.
(a) Speed=\frac{Distance}{Time}
(b) Speed=\frac{Time}{Distance}
(c) Speed=Distance \times Time
(d) None of these
Show Answer
Correct Option: (a) Speed=\frac{Distance}{Time}
Explanation:
Speed is calculated by dividing the distance traveled by the time taken.
(a) F
(b) s
(c) v
(d) d
Show Answer
Correct Option: (c) v
Explanation:
Speed is typically denoted by the symbol ‘v‘ in equations.
Types of Speed
(33). Which type of speed remains constant throughout the motion?(a) Average speed
(b) Instantaneous speed
(c) Uniform speed
(d) Variable speed
Show Answer
Correct Option: (c) Uniform speed
Explanation:
Uniform speed refers to a constant speed maintained throughout the motion.
(a) Average speed
(b) Instantaneous speed
(c) Uniform speed
(d) Variable speed
Show Answer
Correct Option: (a) Average speed
Explanation:
Average speed is calculated by dividing the total distance traveled by the total time taken.
(a) Average speed
(b) Instantaneous speed
(c) Uniform speed
(d) Variable speed
Show Answer
Correct Option: (b) Instantaneous speed
Explanation:
Instantaneous speed is the speed of an object at a specific moment in time.
(a) Average speed
(b) Instantaneous speed
(c) Uniform speed
(d) Variable speed
Show Answer
Correct Option: (b) Instantaneous speed
Explanation:
A speedometer indicates the instantaneous speed of a car at any given moment.
(a) 50 \, \text{km/h}
(b) 100 \, \text{km/h}
(c) 150 \, \text{km/h}
(d) 200 \, \text{km/h}
Show Answer
Correct Option: (a) 50 \, \text{km/h}
Explanation:
Average speed is calculated by dividing the total distance by the total time.
Calculation:
\text{Average speed} = \frac{\text{Total distance}}{\text{Total time}}
\text{Average speed} = \frac{100 \, \text{km}}{2 \, \text{h}} = 50 \, \text{km/h}
(a) 3 \times 10^5 \, \text{m/s}
(b) 3 \times 10^8 \, \text{m/s}
(c) 3 \times 10^3 \, \text{m/s}
(d) 3 \times 10^{12} \, \text{m/s}
Show Answer
Correct Option: (b) 3 \times 10^8 \, \text{m/s}
Explanation:
The speed of light is approximately 3 \times 10^8 \, \text{m/s} .
(a) \text{Speed} = \text{distance} \times \text{time}
(b) \text{Speed} = \frac{\text{total distance traveled}}{\text{total time taken}}
(c) \text{Speed} = \text{final velocity} - \text{initial velocity}
(d) None of these
Show Answer
Correct Option: (b) \text{Speed} = \frac{\text{total distance traveled}}{\text{total time taken}}
Explanation:
Average speed is calculated by dividing the total distance traveled by the total time taken.
Velocity
(40). The displacement covered by a body in unit time is known as:(a) Velocity
(b) Speed
(c) Distance
(d) Displacement
Show Answer
Correct Option: (a) Velocity
Explanation:
Velocity is the displacement covered by a body in unit time and is a vector quantity. Velocity specifies both the speed and direction of motion.
For example, if an object moves 5 m east in 1 second, its velocity is 5 m/s east.
(a) meters per second (m/s)
(b) kilometers per hour (km/h)
(c) Meter
(d) Second
Show Answer
Correct Option: (a) meters per second (m/s)
Explanation:
The SI unit of velocity is meters per second.
For example, if an object travels 20 meters in 4 seconds, its velocity is 20 m / 4 s = 5 m/s.
(a) Scalar
(b) Vector
(c) Tensor
(d) None of these
Show Answer
Correct Option: (b) Vector
Explanation:
Velocity is a vector quantity as it has both magnitude and direction.
(a) \text{Velocity} = \frac{\text{Displacement}}{\text{Time}}
(b) \text{Velocity} = \frac{\text{Time}}{\text{Displacement}}
(c) \text{Velocity} = \text{Distance} \times \text{Time}
(d) None of these
Show Answer
Correct Option: (a) \text{Velocity} = \frac{\text{Displacement}}{\text{Time}}
Explanation:
Velocity is the rate of change of displacement with respect to time.
For example, if an object moves 10 \, \text{m} east in 2 \, \text{s} , its velocity is:
\text{Velocity} = \frac{10 \, \text{m}}{2 \, \text{s}} = 5 \, \text{m/s} \, \text{east}
(a) F
(b) s
(c) \vec{v}
(d) d
Show Answer
Correct Option: (c) \vec{v}
Explanation:
Velocity is typically denoted by the symbol \vec{v} in equations.
Types of Velocity
(45). Which type of velocity remains constant throughout the motion?(a) Average velocity
(b) Instantaneous velocity
(c) Uniform velocity
(d) Variable velocity
Show Answer
Correct Option: (c) Uniform velocity
Explanation:
Uniform velocity refers to a constant velocity maintained throughout the motion.
Uniform velocity implies motion in a straight line without change in speed or direction.
(a) Average velocity
(b) Instantaneous velocity
(c) Uniform velocity
(d) Variable velocity
Show Answer
Correct Option: (a) Average velocity
Explanation:
Average velocity is calculated by dividing the total displacement by the total time taken.
(a) Average velocity
(b) Instantaneous velocity
(c) Uniform velocity
(d) Variable velocity
Show Answer
Correct Option: (b) Instantaneous velocity
Explanation:
Instantaneous velocity is the velocity of an object at a specific moment in time.
(a) \text{Velocity} = \text{displacement} \times \text{time}
(b) \text{Velocity} = \frac{\text{total displacement}}{\text{total time taken}}
(c) \text{Velocity} = \text{final velocity} - \text{initial velocity}
(d) None of these
Show Answer
Correct Option: (b) \text{Velocity} = \frac{\text{total displacement}}{\text{total time taken}}
Explanation:
Average velocity is calculated by dividing the total displacement by the total time taken.
(a) Speed
(b) Velocity
(c) Distance
(d) Time
Show Answer
Correct Option: (b) Velocity
Explanation:
Velocity has both magnitude (speed) and direction.
(a) 350 meters north
(b) 50 meters south
(c) 50 meters north
(d) 350 meters south
Show Answer
Correct Option: (c) 50 meters north
Explanation:
Displacement is the straight-line distance between the initial and final positions, so the train’s displacement is 50 meters north.
Displacement = Final position – Initial position
Displacement = 200 m north – 150 m south
Displacement = 50 m north.
Acceleration
(51). The rate of change in velocity is known as:(a) Velocity
(b) Speed
(c) Acceleration
(d) Displacement
Show Answer
Correct Option: (c) Acceleration
Explanation:
Acceleration is the rate of change of velocity with respect to time.
(a) meters per second (m/s^2)
(b) kilometers per hour (km/h^2)
(c) Meter
(d) Second
Show Answer
Correct Option: (a) meters per second (m/s^2)
Explanation:
Acceleration is measured in meters per second squared.
For example, if an object increases its velocity by 10 \ m/s in 2 \ seconds, its acceleration is:
a=\frac{10 \ m/s}{2 \ s}
a= 10 \ m/s^2
(a) Scalar
(b) Vector
(c) Tensor
(d) None of these
Show Answer
Correct Option: (b) Vector
Explanation:
Acceleration is a vector quantity as it has both magnitude and direction.
(a) Acceleration =\frac{\text{Change in velocity}}{\text{Time}}
(b) Acceleration =\frac{\text{Time}}{\text{Velocity}}
(c) Acceleration =\text{Distance} \times \text{Time}
(d) None of these
Show Answer
Correct Option: (a) Acceleration =\frac{\text{Change in velocity}}{\text{Time}}
Explanation:
Acceleration is the change in velocity divided by the time taken.
\text{Acceleration} = \frac{\text{Final velocity} - \text{Initial velocity}}{\text{Time}}
For example, if an object’s velocity increases from 10 m/s to 20 m/s in 2 seconds, its acceleration is:
a = \frac{20 \, \text{m/s} - 10 \, \text{m/s}}{2 \, \text{s}}
a = 5 \, \text{m/s}^2
(a) F
(b) s
(c) a
(d) d
Show Answer
Correct Option: (c) a
Explanation:
Acceleration is typically denoted by the symbol ‘a‘ in equations.
Types of Acceleration
(56). Which type of Acceleration remains constant throughout the motion?(a) Average Acceleration
(b) Instantaneous Acceleration
(c) Uniform Acceleration
(d) Variable Acceleration
Show Answer
Correct Option: (c) Uniform Acceleration
Explanation:
Uniform acceleration refers to constant acceleration maintained throughout the motion.
An example of uniform acceleration is free-fall under gravity, where the acceleration due to gravity remains constant at 9.8 \ m/s^2.
(a) Average Acceleration
(b) Instantaneous Acceleration
(c) Uniform Acceleration
(d) Variable Acceleration
Show Answer
Correct Option: (a) Average Acceleration
Explanation:
Average acceleration is calculated by dividing the total change in velocity by the total time taken.
(a) Average acceleration
(b) Instantaneous acceleration
(c) Uniform acceleration
(d) Variable acceleration
Show Answer
Correct Option: (b) Instantaneous Acceleration
Explanation:
Instantaneous acceleration is the acceleration of an object at a specific moment in time.
(a) Acceleration = displacement \times time
(b) Acceleration = \frac{total \ change \ in \ velocity}{total \ time \ taken}
(c) Acceleration = final \ velocity - initial \ velocity
(d) None of these
Show Answer
Correct Option: (b) Acceleration = \frac{total \ change \ in \ velocity}{total \ time \ taken}
Explanation:
Average acceleration is calculated by dividing the total change in velocity by the total time taken.
(a) Speed
(b) Acceleration
(c) Distance
(d) Time
Show Answer
Correct Option: (b) Acceleration
Explanation:
Acceleration has both magnitude and direction.
For example, a car moving north and increasing its speed exhibits acceleration in the northward direction.
(a) 9 \ m/s
(b) 15 \ m/s
(c) 4 \ m/s
(d) 20 \ m/s
Show Answer
Correct Option: (b) 15 \ m/s
Explanation:
As a = \frac{\Delta v}{t}
a \times t = \Delta v
\Delta v = 5 \, \text{m/s}^2 \times 4 \, \text{s}
\Delta v = 20 \, \text{m/s}
The object’s velocity increases by 20 \, \text{m/s} after 4 \, \text{seconds} .
Deceleration/ Retardation
(62). When an object slows down, its acceleration is called:(a) Uniform acceleration
(b) Non uniform acceleration
(c) Deceleration
(d) None of these
Show Answer
Correct Option: (c) Deceleration
Explanation:
When an object slows down, its acceleration is in the opposite direction of its velocity, and it is commonly referred to as deceleration.
Distance Time Graph
(63). Which graph represents the relationship between distance traveled and time elapsed?(a) Velocity time graph
(b) Speed time graph
(c) Acceleration time graph
(d) Distance time graph
Show Answer
Correct Option: (d) Distance time graph
Explanation:
The distance time graph represents the relationship between the distance traveled and the time elapsed.
(a) Speed
(b) Velocity
(c) Time
(d) Acceleration
Show Answer
Correct Option: (a) Speed
Explanation:
The slope of a distance time graph represents the speed of the object. The steeper the slope, the greater the speed.
(a) The object is not moving
(b) The object is moving with constant speed
(c) The object is moving with variable speed
(d) The object is accelerating
Show Answer
Correct Option: (a) The object is not moving
Explanation:
A slope of zero in a distance time graph indicates that the object is not moving because there is no change in distance with respect to time.
(a) Zero speed
(b) Uniform speed
(c) Variable speed
(d) None of these
Show Answer
Correct Option: (b) Uniform speed
Explanation:
When the distance increases linearly with time, the body is moving with a constant or uniform speed.
Example:
A car traveling at a constant speed of 50 km/h will produce a straight line on a distance-time graph.
(a) Zero speed
(b) Uniform speed
(c) Variable speed
(d) None of these
Show Answer
Correct Option: (c) Variable speed
Explanation:
When the distance changes nonlinearly with time, the body is moving with variable speed.
Speed Time Graph
(68). Which graph represents the relationship between speed and time elapsed?(a) Velocity time graph
(b) Speed time graph
(c) Acceleration time graph
(d) Distance time graph
Show Answer
Correct Option: (b) Speed time graph
Explanation:
The speed time graph represents the relationship between speed and time.
(a) Speed
(b) Velocity
(c) Time
(d) Magnitude of Acceleration
Show Answer
Correct Option: (d) Magnitude of Acceleration
Explanation:
The slope of a speed time graph represents the magnitude of acceleration.
(a) Speed
(b) Distance
(c) Time
(d) Displacement
Show Answer
Correct Option: (b) Distance
Explanation:
The area under the curve in a speed time graph represents the distance traveled by the object.
If an object moves at 10 m/s for 5 seconds, the area under the graph (rectangle) is 10 \, \text{m/s} \times 5 \, \text{s} = 50 \, \text{m} .
Velocity Time Graph
(71). Which graph represents the relationship between velocity and time elapsed?(a) Velocity time graph
(b) Speed time graph
(c) Acceleration time graph
(d) Distance time graph
Show Answer
Correct Option: (a) Velocity time graph
Explanation:
The graph representing the relationship between velocity and time elapsed is called a velocity time graph.
(a) Speed
(b) Velocity
(c) Time
(d) Acceleration
Show Answer
Correct Option: (d) Acceleration
Explanation:
In a velocity time graph, the slope represents acceleration. The steeper the slope, the greater the acceleration.
(a) Speed
(b) Distance
(c) Time
(d) Displacement
Show Answer
Correct Option: (b) Distance
Explanation:
The area under the curve in a velocity time graph represents the distance traveled.
Equations of Motion
(74). There are …………. equations of motion.(a) 2
(b) 3
(c) 4
(d) 5
Show Answer
Correct Option: (b) 3
Explanation:
The three equations of motion describe the relationships between initial velocity ( v_i ), final velocity ( v_f ), acceleration ( a ), time ( t ), and displacement ( s ).
First Equation of Motion
(75). Which equation of motion represents the relationship between initial velocity, final velocity, acceleration, and time?(a) First equation of motion
(b) Second equation of motion
(c) Third equation of motion
(d) None of these
Show Answer
Correct Option: (a) First equation of motion
Explanation:
The first equation of motion includes initial velocity ( v_i ), final velocity ( v_f ), acceleration ( a ), and time ( t ).
(a) First equation of motion
(b) Second equation of motion
(c) Third equation of motion
(d) All of these
Show Answer
Correct Option: (b) Second equation of motion
Explanation:
The second equation of motion relates initial velocity (v_i) , displacement (s) , acceleration (a) , and time (t) .
Second Equation of Motion
(77). Which equation of motion represents the relationship between initial velocity, final velocity, acceleration, and displacement?(a) First equation of motion
(b) Second equation of motion
(c) Third equation of motion
(d) All of these
Show Answer
Correct Option: (c) Third equation of motion
Explanation:
The third equation of motion relates initial velocity (v_i) , final velocity (v_f) , acceleration (a) , and displacement (s) .
(a) v_f = v_i + at
(b) s = v_i t + \frac{1}{2} at^2
(c) 2as = v_f^2 - v_i^2
(d) None of these
Show Answer
Correct Option: (a) v_f = v_i + at
Explanation:
The first equation of motion relates initial velocity (v_i) , final velocity (v_f) , acceleration (a) , and time (t) .
Third Equation of Motion
(79). The second equation of motion is given by:(a) v_f = v_i + at
(b) s = v_i t + \frac{1}{2} at^2
(c) 2as = v_f^2 - v_i^2
(d) None of these
Show Answer
Correct Option: (b) s = v_i t + \frac{1}{2} at^2
Explanation:
The second equation of motion relates initial velocity (v_i) , displacement (s) , acceleration (a) ), and time (t) .
(a) v_f = v_i + at
(b) s = v_i t + \frac{1}{2} at^2
(c) 2as = v_f^2 - v_i^2
(d) None of these
Show Answer
Correct Option: (c) 2as = v_f^2 - v_i^2
Explanation:
The third equation of motion relates initial velocity (v_i) , final velocity (v_f) , acceleration (a) ), and displacement (s) .
(a) Area = (sum of parallel sides) × base
(b) Area = base × (sum of parallel sides) / 2
(c) Area = base / (sum of parallel sides)
(d) None of these
Show Answer
Correct Option: (b) Area = base × (sum of parallel sides) / 2
Explanation:
The correct formula for the area of a trapezoid is \frac{1}{2} \cdot (a + b) \cdot h , where a and b are the lengths of the parallel sides, and h is the height.
Example:
If a = 5 \ cm , b = 7 \ cm , and h = 4 \ cm :
\text{Area} = \frac{1}{2} \times (5 + 7) \times 4 = 24 \, \text{cm}^2
Motion due to Gravity
(82). The motion of an object falling under the influence of gravity is known as:(a) Uniform motion
(b) Free fall
(c) Circular motion
(d) Rotatory motion
Show Answer
Correct Option: (b) Free fall
Explanation:
Free fall is the motion of an object falling under the influence of gravity alone.
(a) Zero
(b) Negative
(c) Positive and constant
(d) Positive but varying
Show Answer
Correct Option: (c) Positive and constant
Explanation:
During free fall, the acceleration of the object is constant and directed towards the Earth, making it positive.
Near the Earth’s surface, this constant acceleration is g = 9.8 \, \text{m/s}^2 .
(a) Motion of an object along a straight line
(b) Motion of an object under the influence of gravity only
(c) Motion of an object around an axis
(d) Motion of an object in a circular path
Show Answer
Correct Option: (b) Motion of an object under the influence of gravity only
Explanation:
Free fall refers to the motion of an object under the influence of gravity alone, without any other forces acting on it.
(a) v_f = v_i + at
(b) s = v_i t + \frac{1}{2} at^2
(c) 2as = v_f^2 - v_i^2
(d) h = \frac{1}{2} g t^2
Show Answer
Correct Option: (d) h = \frac{1}{2} g t^2
Explanation:
In the case of free falling due to gravity, replace acceleration “a” with acceleration due to gravity “g” and distance “s” with height “h”.
For free-fall motion:
h = \frac{1}{2} g t^2
Example:
If g = 9.8 \, \text{m/s}^2 and t = 2 \, \text{s} :
h = \frac{1}{2} \cdot 9.8 \cdot (2)^2 = 19.6 \, \text{m}.
(a) It experiences zero acceleration
(b) Its acceleration is directed upwards
(c) Its acceleration is directed downwards
(d) It experiences uniform motion
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Correct Option: (c) Its acceleration is directed downwards
Explanation:
An object in free fall near the surface of the Earth experiences acceleration due to gravity, which is directed downwards.
(a) Positive
(b) Negative
(c) Zero
(d) None of these
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Correct Option: (a) Positive
Explanation:
Gravitational acceleration is typically considered positive when a body is falling under gravity.
(a) Positive
(b) Negative
(c) Zero
(d) None of these
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Correct Option: (b) Negative
Explanation:
When a body is thrown upward against gravity, its gravitational acceleration is considered negative.
(a) Positive
(b) Negative
(c) Zero
(d) None of these
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Correct Option: (c) Zero
Explanation:
At the highest point of its trajectory, the body momentarily comes to rest, so the final velocity is zero.
(a) 9.8 m/s²
(b) 32 ft/s²
(c) Both A and B
(d) None of these
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Correct Option: (c) Both A and B
Explanation:
The value of gravitational acceleration ‘g’ at sea level is approximately 9.8 m/s² or 32 ft/s².
The value g = 9.8 \, \text{m/s}^2 is used in the metric system, while g = 32 \, \text{ft/s}^2 is used in the imperial system.
Review Exercise Chapter 2
91. The average speed of a bus is 20 ms^{-1} , how far can it travel in 10s?(a) 100 m
(b) 200 m
(c) 150 m
(d) 250 m
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200 m
92. A truck accelerates uniformly from 15 ms^{-1} \ to \ 20 ms^{-1} \ in \ 5 s . Whit is the acceleration of the truck?
(a) 2 ms^{-2}
(b) 1.5 ms^{-2}
(c) 1 ms^{-2}
(d) 2.5 ms^{-2}
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1 ms^{-2}
93. A car moving along a straight line at 20 ms^{-1} under goes an acceleration of 4 ms^{-2} . After 2 s , its speed will be
(a) 28 ms^{-1}
(b) 16 ms^{-1}
(c) 12 ms^{-1}
(d) 8 ms^{-1}
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28 ms^{-1}
94. A bird begins to accelerate a constant 0.3 m/s^2 \ for \ 3 s. its change in velocity is
(a) 0.9 m/s
(b) 15.m/s
(c) 1.95 m/s
(d) 2.4 m/s
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0.9 m/s
95. A car is going backward at 5 m/s . After 10 s of uniform acceleration, the car is going forward at 10 m/s . The acceleration is:
(a) 0.5 m/s^2
(b) 0.75 m/s^2
(c) 1.5 m/s^2
(d) 4 m/s^2
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1.5 m/s^2
96. The slope of distance – time graph represents:
(a) Acceleration
(b) Change in acceleration
(c) Speed
(d) Distance
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Speed
97. The area under a speed – time graph represents:
(a) Acceleration
(b) Change in acceleration
(c) Distance
(d) Velocity
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Distance
98. A student is riding his bicycle on a straight flat road covers one block every 7 seconds. If each block is 100m long, he is traveling at:
(a) Constant speed
(b) Constant velocity
(c) 10m/s
(d) Both (a) & (b)
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Both (a) & (b)
99. You drop a rock from a bridge to the river below. When the rock has fallen 4 m, you drop a second rock. As the rocks continue their free fall, their separation
(a) Increase
(b) Decrease
(c) Stay the same
(d) None of these
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Stay the same
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