Class 9 physics chapter 1 physics
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The document discusses the concept of motion, defining it as a change in position over time and distinguishing between scalar and vector quantities. It covers types of motion (uniform and non-uniform), the importance of reference points, and introduces speed and velocity as measures of motion. Additionally, it explains the graphical representation of motion using distance-time and velocity-time graphs.
Class 9 physics chapter 1 physics
- 2. Introduction ❏ In our daily life, we see some object at rest and other in Motion. ❏ 🐦 Bird's fly, fishes swim, blood flows through vein and arteries and car moves, these are some examples of the State of Motion. ❏ Motion is a state of body if it's position changes with respect to the Time. ❏ There are also situation where the Motion is inferred through indirect evidences. ❏ An object may appear to be moving for one person and stationary for some other. ❏ In this chapter through the lecture and slide we will study motion in straight line and at last we shall discuss the circular motion. This is a reference image to show Motion.
- 3. Physical Quantity Scalar Quantity The quantity having only magnitude it is said to be Scalar Quantity. ❏ Mass ❏ Distance ❏ Speed ❏ Time ❏ Temperature ❏ Boiling point ❏ Density ❏ Work ❏ Energy, etc. Vector Quantity The quantity having both magnitude as well as the direction it is said to be Vector Quantity. ❏ Displacement ❏ Velocity ❏ Acceleration ❏ Force ❏ Momentum ❏ Torque, etc.
- 4. To describe the position of an object we needto specify reference point called the origin.
- 5. Motion along a straight line ❏ The simplest type of Motion is the Motion along a straight line. ❏ For Example- If a object start it's journey he travelled from O to C, then C to B, then B to A. ❏ The total path covered by a an object is called the total distance covered. ❏ The shortest distance between any two positions. ❏ In next slide we will go through difference between Total dis covered and Displacement.
- 6. Difference between the total distance and Displacement Total distance covered ❏ Total Distance ❏ The value of Distance covered is only positive. ❏ It can not be zero. ❏ It is a Scalars Quantity. Displacement ❏ Shortest Distance ❏ The value of Displacement may be positive or negative. ❏ It can be zero. ❏ It is a Vector Quantity.
- 7. Uniform Motion And Non Uniform Motion Uniform Motion ❏ If the object covers equal distance in equal interval of time, It is said to be in Uniform Motion. ❏ For example :- ❏ If a object covers 50 km in first hour and again 50 km in next hour, then it is a Uniform Motion. Non Uniform Motion ❏ If a object covers unequal distance in equal interval of time, it is said to be Non - Uniform Motion. ❏ For example :- ❏ If a object covers 50 km in first hour and again 30 km in next hour, then it a Non Uniform Motion.
- 8. Measuring the Rate of Motion ❏ The ways of measuring the rate of motion of an object is to find out the distance travelled by the object in unit time. This quantity is referred as speed. ❏ The SI unit of speed is metre per second. ❏ This is represented by the symbol m/sec. ❏ The other units are cm/sec, km/h. ❏ To specify the speed of an object, we require only it's magnitude. ❏ The speed of object need not to be constant. ❏ in most cases object will be in non uniform motion. ❏ Therefore we describe the rate of motion of such objecys in terms of average speed. ❏ The average speed of an object is obtained by dividing the total distance travelled by the total time taken i.e.
- 9. Speed With Direction ❏ The rate of motion of an object can be more comprehensive if we specify its direction of motion along with speed. ❏ The quantity that specifies both this aspect is called velocity. ❏ Velocity is the speed of an object moving in a definite direction. ❏ The velocity of an object can be uniform or variable it can be changed by changing the object speed direction of the motion or both. ❏ When an object is moving in a straight line at a variable speed we can express the magnitude of its rate of motion in terms of average velocity. ❏ It is calculated in the same way as we calculate the average speed. ❏ In this case the velocity of the object is changing at a uniform rate, then average velocity is given by arithmetic mean of initial velocity and final velocity for a given period of time that is,
- 10. Rate of Change of Velocity ❏ During uniform motion of an object along a straight line, the velocity remains constant with time. In this case the change in velocity of object for any time interval is zero. ❏ In non uniform motion, velocity varies with time. It has different value at different instant and different points of the path. ❏ Thus, change in velocity of object during any time interval is not zero. ❏ At this time we introduce a new physical quantity that is acceleration. ❏ Acceleration is the measure of change in the velocity of an object per unit time that is,
- 12. Graphical Representation of Motion Distance - Time Graph ❏ The change in the position of an object which time can be represented on the distance time graph adopting a convenient scale of choice. ❏ In this graph, time is taken along the x axis and distance taken along the y axis. ❏ Distance time graph can be employed under the various conditions where objects move with uniform speed, non uniform speed, remains at rest, etc.
- 14. Graphical Representation of Motion Velocity - Time Graph ❏ The variation in velocity with time for an object moving in a straight line can be represented by a velocity time graph. ❏ In this graph, time is represented along the x-axis and the velocity is represented along the y axis. ❏ If the object moves at uniform velocity the height of its velocity time graph will not change with time. It will be straight line parallel to x axis shown in fig. 8.5
- 18. Equation of Motion by Graphical Method
- 26. Uniform Circular Motion ❏ When the velocity of an object changes we say that object is accelerating. the change in velocity could be due to the change in its magnitude or the direction of the motion or the both. ❏
- 27. THANK YOU