Post on 04-Jul-2015
description
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SIMULATIONS :
http://hypertextbook.com/physics/mechanics/displacement/
(distance & displacement)
http://regentsprep.org/Regents/physics/phys01/velocity/default.htm
(distance & displacement – ant)
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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
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DIFFERENCES BETWEEN DISTANCE & DISPLACEMENT
B
A
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B
distance
displacement
A
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DISTANCE AND DISPLACEMENT
Total length travelled from point A to point B
Total distance travelled in a specified direction
A
B
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DISTANCE The total path length travelled from
one location to another Scalar quantity SI unit : m
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DISPLACEMENT The distance between two location
measured along the shortest path
connecting them in a specified
direction Vector quantity SI unit : m
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SPEED & vELoCITy
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SPEED The rate of change of distance
Average speed = total distance travelled, s
time, t
Scalar quantity SI unit : ms-1
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The rate of change of displacement
Average velocity = total displacement , s
time, t
Vector quantity SI unit : ms-1
vELoCITy
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ISTANTANEoUS SPEED :
The speed at any instant
ISTANTANEoUS vELoCITy :
The velocity at any instant
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http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/kinema/trip.html
(average speed)
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APPLICATIoN :
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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
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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
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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)
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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
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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