MOTION

Life is a full circle, widening until it joins the circle motions of the infiniteMOTION

Made by Mridul verma of class 9 a section a1

What is Motion

Motion :- It is the change in position of a body with time. Motion can be described in terms of the distance moved or the displacement.

Concept :- Inphysics,motionis a change inpositionof an object with respect to time. Motion is typically described in terms ofdisplacement,distance,velocity,acceleration,timeandspeed. Motion of a body is observed by attaching a frame of referenceto an observer and measuring the change in position of the body relative to that frame.

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DISTANCE Distance moved :- It is the actual length of the path travelled by a body.

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Total Distance covered in ONE LAP = 400mStarting & Ending point

DISPLACEMENTDisplacement :- It is the length of the shortest path travelled by a body from its initial position to its final position. Mridul Verma | 9 "A" | 105

Total displacement in ONE LAP = 0Starting & ending point

SPEEDSpeed :- Speed of a body is the distance travelled by the body in unit time. Speed = Distance TimeIf a body travels a distance s in time t then its speed v is v = s t The SI unit of speed is metre per second m/s or ms -1 Since speed has only magnitude it is a scalar quantity.

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VELOCITYThe rate of motion of a body is more meaningful if we specify its direction of motion along with speed. The quantity which specifies both the direction of motion and speed is velocity.Velocity :- Velocity of a body is the displacement of the body per unit time. Velocity = Displacement Time taken Since velocity has both magnitude and direction, it is a vector quantity.

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ACCELERATION The quantity which specifies changes in velocity is acceleration.Acceleration :- It is the change in velocity of a body per unit time. ( or the rate of change of velocity.) Acceleration = Change in velocity Time If the velocity of a body changes from initial value u to final value v in time t, then acceleration a is a = v - u t .The SI unit of acceleration is ms - 2

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PLOTTING POINTSMridul Verma | 9 "A" | 109We already know how to plot points on a graph. So let`s recall them. Suppose I want to plot points (3, 4) on a graph, it will be as follows :-01234512345YX

Points to plot (3, 4)X = 3Y = 4In this similar way, we can plot many other points on a graph.

GRAPHS AND ITS TYPESA graph is a pictorial representation of observation. It consist of two variables, one is independent variable and other is dependent variable.Independent variable is taken along X-axis and dependent variable is taken along Y-axis.There are many types of graphs in physics, some of them are as follows :- 1. Distance time graph 2. Displacement time graph 3. Velocity time graph 4. Acceleration time graphMridul Verma | 9 "A" | 1010

DISTANCE TIME GRAPHThe change in the position of a body with time can be represented on the distance time graph. In this graph distance is taken on the Y axis and time is taken on the X axis. The distance time graph for uniform speed is a straight line ( linear ). This is because in uniform speed a body travels equal distances in equal intervals of time. We can determine the speed of the body from the distance time graph. They are used to find speed or velocity of body.The slope of it gives speed of body.

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Mridul Verma | 9 "A" | 1012 There are 3Types of distance time graphs.When body is at rest It`s a straight line parallel to time axis.td2. When body is mpving with uniform speed when the body is moving with uniform speed the graph is a straight line making an angle with the time axis and the slope of this graph is given by - slope = Y2 Y1 / X2 X1 which is equal to speed.td

Mridul Verma | 9 "A" | 10133. When a body is moving with Non uniform speed The body covers unequal distances in equal intervals of time.tdtd

decreasing speedincreasing speedThese curves are called parabola.So, greater the angle, greater is the slope and greater is the speed

DISPLACEMENT TIME GRAPHMridul Verma | 9 "A" | 1014It is a vector quantity and it`s slope gives velocity.There are 3-Types of displacement time graph, they are as follows :- 1. When body is at rest -tsSlope of this graph is 0.

Mridul Verma | 9 "A" | 10152. Body moving with uniform speed -ts

Q1Q2ABWhere Q1 > Q2 Velocity of A > Velocity of B3. Body moving with variable/non uniform velocity -ts

velocity increasess

velocitydecreasest

VELOCITY TIME GRAPHMridul Verma | 9 "A" | 1016For a body moving in straight line, without changing it`s direction, velocity of body becomes equal to it`s speed.The slope of velocity time graph gives acceleration of body.The area under this graph gives the value of distance travelled.There are 3 different cases of this graph, which we have discussed next -

Mridul Verma | 9 "A" | 1017CASE - IIf the body is moving with constant speed.tvSlope = 0Acceleration = ms - 2

Constant speed If the body moves with constant velocity/speed then graph is straightline parallel to time axis and slpoe and acceleration will be 0.

Mridul Verma | 9 "A" | 1018CASE - IIWhen a body is moving with uniformly changing speed -a.) If speed increases uniformly.vtThis slope is known as positive slope and slope givesuniform acceleration.b.) If speed is decreasing uniformly -vtThe graph is straight line slope downwards. Hence, the slope isnegative. The slope of this graph gives retardation.Area in both cases (a & b) gives distance travelled by body.

Mridul Verma | 9 "A" | 1019CASE - IIINon uniformly changing speed.a.) If speed increases non uniformly.v

tThe graph is a curve moving upward. The slope of tangentdrawn at any point on curve is positive and is equal to acceleration of body.b.) If speed decreases non uniformly.tv

The graph is a curve moving downwards and the slope oftangent is negative and gives the value of retardation.

ACCELERATION TIME GRAPHMridul Verma | 9 "A" | 1020The graph is as shown below -CASE - IVtFor a body at rest -Acceleration is 0 for a body at rest or when is moves with uniform speedCASE - IIFor a body moving with uniform acceleration.slope = 0ta-aslope = 0In uniform acceleration the acceleration is constant anddoes not change and hence the graph is straight line parallel to time axis.

EQUATIONS OF MOTION BY GRAPHICAL METHODMridul Verma | 9 "A" | 1021The motion of a body moving with uniform acceleration can be described with the help of three equations called equations of motion.The equations of motion are :- i) v = u + at ii) s = ut + at2 iii) 2as = v2 u2 Where u - is the initial velocity v - is the final velocity a - is acceleration t - is the time s - is the distance traveled

CIRCULAR MOTIONMridul Verma | 9 "A" | 1022The motion of a body in a circular path is called circular motion.Uniform circular motion :- If a body moves in a circular path with uniform speed, its motion is called uniform circular motion.Uniform circular motion is accelerated motion because in a circular motion a body continuously changes its direction.The circumference of a circle of radius r is given by 2r. If a body takes time t to go once around the circular path, then the velocity v is given by v = 2r t

Mridul Verma | 9 "A" | 1023Thanks for watching.Name Mridul VermaClass 9 ARoll No. - 10Mridul Verma

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