speed & velocity

3

SIMULATIONS :

http://hypertextbook.com/physics/mechanics/displacement/

(distance & displacement)

http://regentsprep.org/Regents/physics/phys01/velocity/default.htm

(distance & displacement – ant)

4

A car is moving towards North

A snake is crawling

Speed limit on the highway in Malaysiais 110 kmh-1

An athlete is moving towards the checkpoint at a velocity of 25 ms-1

5

DIFFERENCES BETWEEN DISTANCE & DISPLACEMENT

B

A

6

B

distance

displacement

A

7

DISTANCE AND DISPLACEMENT

Total length travelled from point A to point B

Total distance travelled in a specified direction

A

B

8

DISTANCE The total path length travelled from

one location to another Scalar quantity SI unit : m

9

DISPLACEMENT The distance between two location

measured along the shortest path

connecting them in a specified

direction Vector quantity SI unit : m

10

SPEED & vELoCITy

11

SPEED The rate of change of distance

Average speed = total distance travelled, s

time, t

Scalar quantity SI unit : ms-1

12

The rate of change of displacement

Average velocity = total displacement , s

time, t

Vector quantity SI unit : ms-1

vELoCITy

13

ISTANTANEoUS SPEED :

The speed at any instant

ISTANTANEoUS vELoCITy :

The velocity at any instant

14

http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/kinema/trip.html

(average speed)

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APPLICATIoN :

16

QUESTIoN 1 :

A cow moves 3 m to the East and the

4 m to the North. Find the :

(a) Total distance moved by the cow

(b) Displacement of the cow

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North East

West East

North

South

South East

North West

South West

DIRECTION

18

ANSWER 1 :

A B

C

3 m

4 m

(a)The total distance moved by the cow

= 3 m + 4 m

= 7 m

(b) Displacement of the cow

= √32 + 42

= 5 m due to North East

19

QUESTION 2 :

O A

BFigure shows the path travelled by a

cyclist. He started his journey from O, moved a distance of 150 m to East towards A and then moved a distance of 200 m to North towards B. The cyclist took about 25 s to complete his journey. Determine :

(a) The total distance travelled

(b) The displacement from O

(c) The average speed of the cyclist

(d) The average velocity of the cyclist

150 m

200 m

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O A

B

150 m

200 m

ANSWERS 2 :

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(a) Total distance travelled

= 150 m + 200 m

= 350 m

(b) Displacement

= √1502 + 2002

= 250 m due North East

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(c) Average speed

= 350 m

25 s

= 14 ms-1

(d) Average velocity

= 250 m

25 s

= 10 ms-1

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REFLECTION / CLOSURE (EVALUATION)

24

DIFFERENCES BETWEEN DISTANCE & DISPLACEMENT :

DISTANCE DISPLACEMENT

The total path length travelled from one location to another

The distance between two location measured along the shortest path connecting them in a specified direction

Scalar quantity Vector quantity

SI unit : metre SI unit : metre

25

DIFFERENCES BETWEEN SpEED & vEloCITy :

SPEED VELOCITY

The rate of change of distance

The rate of change of displacement

Scalar quantity Vector quantity

Average speed = total distance travelled, s time, t

Average velocity = total displacement , s time, t

SI unit : ms-1 SI unit :ms-1