class 14 KINEMATICS€¦ · class 14 KINEMATICS Author: Rishi Gopie Created Date: 9/24/2014 12:56:03 AM

KINEMATICS: LINEAR MOTION PHYSICS

Mr Rishi Gopie

Mr R Gopie KINEMATICS: LINEAR MOTION

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KINEMATICS: LINEAR MOTION

Definitions of quantity

Distance: is defined as the length of the path taken between two points

Displacement: is defined as the linear distance between two points in a specific direction

Speed: is defined as the rate of change of distance with time s = Distance/ time (d/t)

Velocity: is defined as the rate of change of displacement with time

Velocity = displacement/ time

Acceleration: is defined as the rate of change of velocity with time.

Quantity Typical Symbol Unit Symbol

Distance/ displacement s ( or x) m

time t s

initial speed/ velocity u ms^-‐1

final speed/ velocity v ms^-‐1

acceleration a ms^-‐2


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Equations of motion

These equations apply to uniformly accelerated linear motion

1) Uniform (i.e. constant) speed/velocity = distance/ time

2) Acceleration, a = velocity change / time for change i.e. a = v-‐u/t

ð v = u + at ; t = v-‐u/a ; u = v –at

3) s = ut + ½at²

4) v² = u² + 2as

5) u² = v² -‐ 2as

6) a = v² -‐ u²/2s

7) s = v² -‐ u²/ 2a

Average speed/ velocity = u + v/ 2

Total distance (displacement)/ total time taken

= s/t


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Graphs of motion

a) displacement – time (i.e. s-‐t) graphs

From such graphs, the following can be determined

i) displacement – from the s axis

ii) time – from the t axis

iii) velocity/speed – from the gradient (i.e. slope) of the graph

Where ‘m’ = vertical rise / horizontal run

Note that a positive gradient/ slope indicate motion away from some reference point/ location while a negative gradient/ slope indicates motion towards the reference point.


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Diag. 17 -‐ 21


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b) velocity – time (i.e. v-‐t) graphs

From such graphs the following can be obtained

i) velocity/speed – from the v-‐axis

ii) time – from the t-‐axis

iii) acceleration – from the gradient/slope of graph

Note that a positive gradient indicates acceleration, while a negative gradient indicates deceleration (or retardation)

iv) Displacement-‐ from the area under the graph unto the t-‐axis ( in a given time interval). In certain situations (such as when the area is under a curve and is therefore irregular in shape, the area has to be estimated ( say, by a method involving checking squares on graph paper or grid lines-‐ where estimated area Ξ number of squares estimated x area of each square (in terms of the scales used)


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Diag. 30


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TUTORIAL

June 1998 paper 3 # 3


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January 1999 paper 2 #1


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June 2010 paper 2 #2


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class 14 KINEMATICS€¦ · class 14 KINEMATICS Author: Rishi Gopie Created Date: 9/24/2014 12:56:03 AM