MOTION

MADE BY: NIKITA MEHROTRA IX - A

A CAR OR BUS MOVES ON A ROAD , A TRAIN MOVES ON THE TRACK , A SHIP MOVES IN WATER AND AN AEROPLANE MOVES WHEN IT FLIES IN AIR FROM ONE PLACE TO ANOTHER . THE MOVEMANT OF A BODY IS CALLED MOTION . A COMMON CHARACTERISTIC OF ALL THE MOVING BODIES IS THAT THEY CHANGE THEIR POSITION WITH TIME . A BODY IS SAID TO BE IN MOTION WHEN ITS POSITION CHANGES CONTINUOUSLY WTH RESPECT TO A STATIONARY OBJECT TAKEN.FOR EXAMPLE: WHEN A POSITION OF A CAR CHANGES CONTINOUSLY WITH RESPECT TO STATIONARY OBJECTS LIKE HOUSES AND TREES , ETC.

MOTION

UNIFORM AND NON-UNIFORM MOTION

DISTANCES OF 10 A BODY HAS A UNIFORM MOTION IF IT TRAVELS EQUAL DISTANCES IN EQUAL INTERVALS OF TIME . FOR EXAMPLE – A CAR RUNNING AT A CONSTANT SPEED OF SAY, 10 METERS PER SECOND, WILL COVER EQUAL METERS,EVERY SECOND,SO ITS MOTION WILL BE

UNIFORM.

A BODY HAS A NON- UNIFORM MOTION IF IT TRAVELS UNEQUAL INTERVAL DISTANCES IN EQUAL INTERVALS OF TIME.FOR EXAMPLE- IF WE DROP A BALL FROM THE ROOF OF A TALL BUILDING, WE WILL FIND THAT IT COVERS UNEQUAL DISTANCES IN EQUAL INTERVALS OF TIME .

THE MOTION OF A BODY CAN BE DESCRIBED BY THREE TERMS: SPEED,VELOCITY & ACCELERATION

SPEED: IF A CAR IS RUNNING SLOW, WE SAY THAT ITS SPEED IS HIGH.THUS,THE SPEED OF A BODY GIVES US AN IDEA OF HOW SLOW OR FAST THAT BODY IS MOVING.SPEED OF A BODY IS THE DISTANCE TREAVELLED BY IT PER UNIT TIME.•FORMULA FOR SPEED:

VELOCITY: THE SPEED OF A CAR GIVES US AN IDEA OF HOW FAR THE CAR IS MOVING BUT IT DOES NOT TELL US THE DIRECTION IN WHICH THE CAR IS MOVING.THUS, TO KNOW THE EXACT POSITION OF A MOVING CAR WE SHOULD ALSO KNOW THE SPEED OF THE CAR AS WELL AS THE DIRECTION OF SPEED.

FORMULA FOR VELOCITY:

UNIFORM VELOCITY: A BODY HAS A UNIFORM VELOCITY IF IT TRAVELS IN A SPECIFIED DIRECTION IN A STRAIGHT LINE AND MOVES OVER EQUAL DISTANCES IN EQUAL INTERVALS OF TIME.

ACCELERATION: WHEN THE VELOCITY OF A BODY IS INCREASING ,THE BODY IS SAID TO BE ACCELERATING.THE SI UNIT OF ACCELERATION IS “METER PER SECOND PER SECOND”FORMULA FOR ACCERELATION :

UNIFORM ACCELERATION: A BODY HAS A UNIFORM ACCELERATION IF IT TRAVELS IN A STRAIGHT LINE AND ITS VELOCITY INCREASESBY EQUAL AMOUNTS IN EQUAL INTERVALS.

NON-UNIFORM ACCELERATION; A BODY HAS ANON-UNIFORM ACCELERATION IF ITS VELOCITY INCREASES BY UNEQUAL AMOUNTS IN EQUAL INTERVALS OF TIME.A BODY HAS A NON-UNIFORMACCELERATION IF ITS VELOCITY CHANGES AT A NON-UNIFORM RATE.

MOTION ALONG A STRAIGHT LINE

THE SIMPLE TYPE OF MOTION IS THE MOTION ALONG A STRAIGHT LINE.FOR EXAMPLE-

THE OBJECT STARTS ITS JOURNEY FROM O WHICH IS TREATED AS ITS REFERENCE POINT.LET A,B,&C REPRESENT THE POSITION OF THE OBJECT AT DIFFERENT INSTANTS.AT FIRST,THE OBJECTS MOVES THROUGH C&B AND REACHES A.THEN IT MOVES BACK ALONG THE SAME PATH AND REACHES C

THROUGH B.THE TOTAL PATH LENGTH COVERED BY THE OBJECT IS OA+AC,THAT IS 60km+35km=95km.FOR MOTION OF THE OBJECT FROM O TO A,THE DISTANCE COVERED IS 60km AND THE MAGNITUDE OF DISPLACEMENT IS ALSO 60km.DURING ITS MOTION FROM O TO A AND BACK TO B,THE DISTANCE COVERED=60km+25km=85km WHILE THE MAGNIYUDE OF DISPLACEMENT=35km.THUS,THE MAGNITUDE OF DISPLACEMENT(35km) IS NOT EQUAL TO THE PATH LENGTH (85km).FURTHER WE WILL NOTICE THAT THE MAGNITUDE OF DISPLACEMENT FOR A COURSE OF MOTION MAY BE ZERO BUT THE CORRESPONDING DISTANCE COVERED IS NOT ZERO .

IF WE CONSIDER THE OBJECT TO TRAVEL BACK TO O,THE FINAL POSITION CONCIDES WITH THE INITIAL POSITION,AND THEREFORE,THE DISPLACEMENT IS ZERO.HOWEVER ,THE DISTANCE COVERED IN JOURNEY IS OA+AO=60km+60km= 120km.THUS .TWO DIFFERENT PHYSICAL QUANTITIES- THE DISTANCE AND THE DISPLACEMENT,ARE USED TO DESCRIBE THE OVERALL MOTION OF AN OBJECT AND TO LOCATE ITS FINAL POSITION WITH REFERENCE TO ITS INITIAL POSITION AT A GIVEN TIME.

GRAPHICAL REPRESENTATION OF MOTION

GRAPHS PROVIDE A CONVENIENT METHOD TO PRESENT BASIC INFORMATIONABOUT A VARIETY OF EVENTS.FOR EXAMPLE,IN THE TELECAST OF A ONE-DAY CRICKET MATCH,VERTICAL BAR GRAPHS SHOW THE RUN RATE OFA TEAM IN EACH OVER. GRAPHS PROVIDE A CONVENIENT METHOD TO PRESENT BASIC INFORMATION

TO DESCRIBE THE MOTION OF AN OBJECT,WE CAN USE LINE GRAPH.IN THIS CASE,LINE GRAPHS SHOW DEPENDENCE OF ONE PHYSICAL QUANTITY,SUCH AS DISTANCE OR VELOCITY,ON ANOTHER QUANTITY,SUCH AS TIME.

DISTANCE - TIME GRAPHS

THE CHANGE IN THE POSITION OF AN OBJECT WITH TIME CAN BE REPRESENTED ON THE DISTANCE-TIME GRAPH ADOPING A CONVENIENT SCALENOF CHOICE.IN THIS GRAPH,TIME IS TAKEN ALONG THE x-axis AND DISTANCE IS TAKEN ALONG THE y-axis.DISTANCE TIME GRAPHS CAN BE EMPLOYED UNDER VARIOUS CINDITIONS WHERE OBJECTS MOVE WITH UNIFORM SPEED, REMAIN AT REST ETC.

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 REPRESENTED ALONG 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 TIME . IT WILL BE A STRAIGHT LINE PARALLEL TO THE x-axis .

EQUTIONS OF UNIFORMLY ACCELERATED MOTION. 1. FIRST EQUATION OF MOTION

v = u + at . it gives the velocity acquired by body in time.

V=FINAL VELOCITY OF THE BODY U=UNITIAL VELOCITY OF THE BODY A=ACCELERATION T=TIME TAKEN

2.SECOND EQUATION OF MOTION

s = ut + ½ at² IT GIVES THE DISTANCE TRAVELLED BY A BODY IN TIME.

S = DISTANCE TRAVELLED BY THE BODY IN TIME . U = INITIAL VELOCITY OF THE BODY. A = ACCELERATION

T = TIME.

3 . THIRD EQUATION OF MOTION

2as = v ² – u² .

IT GIVES THE VELOCITY ACQUIRED

BY IN TREVELLING A DISTANCE.

V = FINAL VELOCITY U = INITIAL VELOCITY . A = ACCELERATION . S = DISTANCE TRAVELLED.

UNIFORM CIRCULAR MOTION

WHEN A BODY MOVES IN A CIRCLE, IT IS CALLED CIRCULAR MOTION . WHEN THE VELOCITY OF AN OBJECT CHANGES, WE SAY THAT THE OBJECT IS ACCELERATING . THE CHANGE IN THE VELOCITY COULD BE DUE TO CHANGE IN ITS MAGNITUDE OR THE DIRECTION OF THE MOTION OR BOTH .WHEN A BODY MOVES IN A CIRCULAR PATH WITHN UNIFORM SPEED,ITS MOTION IS CALLED UNIFORM CIRCULAR MOTION.

UNIFORM CIRCULAR MOTION

EXAMPLES OF UNIFORM CIRCULAR MOTION

ARTIFICIAL SATELLITES MOVE UNDER UNIFORM CIRCULAR MOTION AROUND THE EARTH.

THE MOON MOVES IN UNIFORM CIRCULAR MOTION AROUND THE EARTH .

THE EARTH MOVES AROUND THE SUN IN UNIFORM CIRCULAR MOTION .

THE TIP OF A SECONDS HAND OF A WATCH EXHIBITS UNIFORM CIRCULAR MOTION ON THE CIRCULAR DIAL OF THE WATCH.

AN ATHLETE MOVING ON A CIRCULAR TRACK WITH A CONSTANT SPEED EXHIBITS UNIFORM CIRCULAR MOTION .