Motion Class 9 Notes | Motion Handwritten notes class 9
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Motion Class 9 Notes | class 9 science chapter 8 notes | Motion Hand Written notes
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Notes of Ch 8 Motion| Class 9th Science
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• Introduction.
• Distance and Displacement.
• Uniform and Non-uniform motion.
• Speed.
• Velocity.
• Accelerated and Decelerated motion.
• Equations of motion.
• Graphical representation of motion.
• Uniform circular motion.
Introduction.
• Rest: A body is said to be in a state of rest when its position does not change with respect to a reference point..
• Motion: A body is said to be in a state of motion when its position change continuously with reference to a point..
→ Motion can be of different types depending upon the type of path by which the object is going through..
(i) Circulatory motion/Circular motion – In a circular path..
(ii) Linear motion – In a straight line path..
(iii) Oscillatory/Vibratory motion – To and fro path with respect to origin..
• Scalar quantity: It is the physical quantity having own magnitude but no direction. Example: distance, speed..
• Vector quantity: It is the physical quantity that requires both magnitude and direction..
Example: displacement, velocity..
Distance and Displacement
→ The actual path or length travelled by a object during its journey from its initial position to its final position is called the distance..
→ Distance is a scalar quantity which requires only magnitude but no direction to explain it..
Example: Ramesh travelled 65 km. (Distance is measured by odometer in vehicles.).
→ Displacement is a vector quantity requiring both magnitude and direction for its explanation..
Example: Ramesh travelled 65 km south-west from Clock Tower..
→ Displacement can be zero (when initial point and final point of motion are same
Difference between Distance and Displacement.
Distance.
Displacement.
Length of actual path travelled by an object.Shortest length between initial point and far point of an object.It is scalar quantity. It is vector quantity.It remains positive, can’t be ‘0’ or negative.It can be positive (+ve), negative (-ve) or zero.Distance can be equal to displacement (in linear
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In Class 9 Science Chapter 8 Motion, students learn to describe the motion of objects along a straight line and express such motions through simple equations and graphs. The chapter also discusses ways of describing circular motion.
Reference Point and Reference Frame
To describe the position of an object, we need a reference point or origin. An object may seem to be moving to one observer and stationary to another.
Example: A passenger inside a bus sees the other passengers to be at rest, whereas an observer outside the bus sees the passengers to be in motion.
In order to make observations easy, a convention or a common reference point or frame is needed. All objects must be in the same reference frame.
Distance and Displacement
The magnitude of the length covered by a moving object is called distance. It has no direction.
Displacement is the shortest distance between two points or the distance between the starting and final positions with respect to time. It has magnitude as well as direction.
Magnitude
Magnitude is the size or extent of a physical quantity. In physics, we have scalar and vector quantities.
Scalar quantities are only expressed as magnitude. E.g.: time, distance, mass, temperature, area, volume
Vector quantities are expressed in magnitude as well as the direction of the object. E.g.: Velocity, displacement, weight, momentum, force, acceleration, etc.
Time, Average Speed and Velocity
Time and speed
Time is the duration of an event that is expressed in seconds. Most physical phenomena occur with respect to time. It is a scalar quantity.
Speed is the rate of change in distance. If a body covers a certain distance in a certain amount of time, its speed is given by
𝑆𝑝𝑒𝑒𝑑=𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒𝑇𝑖𝑚𝑒
The instantaneous speed is the speed of an object at a particular moment in time.
Average speed is stated as the distance covered by the object within a period of time.
Average speed = Total distance travelled / Total time taken
The below table lists the difference between Average Speed and Instantaneous Speed.
be given by a speedometer.