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Friday, April 3, 2009

exam coming ar

*coughs*
So. Next week is exam week and I haven't even started studying.
And I'm on9.
So I might as well find some excuse to be on9 (actually I'm waiting for someone, want to ask her something and don't want to call her. Okok, it's not just her that I'm waiting for. See I'm so honest la.)

PHYSICS: Chapter 2, until Momentum
Linear Motion
-motion in a straight line

Distance -total length traveled -scalar quantity (no magnitude) Displacement -measured along shortest path -vector quantity (magnitude+direction)

*measured in metre

Speed
-rate of change of distance
-distance / time
-v = s / t
-average speed = total distance / time taken
-scalar quantity

Velocity
-rate of change of displacement
-displacement / time
-v = s / t
-vector quantity

Acceleration
-
rate of change of velocity
-(final velocity - initial velocity) / time taken
- a = (v-u)/t
-vector quantity
-constant velocity = zero acceleration


Analysing Linear Motion
Ticker Timer
-50 Hz
-50 dots per second
-time interval between 2 consecutive dots is called a tick
-1 tick = 1/50 seconds = 0.02 seconds
-. . . . . . constant velocity
-. . . . . . constant acceleration
-. . . . . . constant deceleration
u=x1 cm/ 0.02s
v=x2 cm/ 0.02s
t=(n-1) x 0.02s = nt s
acceleration = (v-u)/t

The Equations of Motion
1. v=u+at
2. s=1/2(u+v)t
3. s=ut+1/2 a(t-squared)
4. (v-squared)=(u-squared)+2as

Analaysing Motion Graphs
I)The Displacement-Time Graph
a) *straight line
i) No change in displacement.
ii) Velocity=gradient of the graph = 0

b) *slanting upwards
i) uniform velocity
ii)
Velocity=gradient of the graph

c) *curving upwards [kinda like ) de shape)
i) rate of change of displacement is increasing
ii) velocity is increasing
iii) object is moving with acceleration

d) *triangular shape
i) initially, constant velocity
ii) after that, gradient of graph is negative (negative velocity)
iii) displacement is zero


II) The Velocity-Time Graph
a) *straight line
i) gradient = zero
ii) acceleration = 0
iii) displacement = area under the graph

b) *slanting upwards
i) acceleration is uniform
ii) acceleration = gradient of graph
iii) displacement = area under the graph

c) *slanting downwards
i) deceleration is uniform
ii) "
iii) "

d) *curving upwards [turn ) anticlockwise about 45 degrees]
i) acceleration of the object is increasing

e) *curving upwards [turn ( clockwise about 45 degrees]
i) acceleration of the object is decreasing

Inertia
-tendency of an object to remain at rest
-if moving, to continue its uniform motion in a straight line

Mass and Inertia
-
the larger the mass, the larger its inertia

*skates over effects of inertia, coz too long to type out*

Analysing Momentum
-
momentum = mass x velocity
-p = mv

The Principle of Conservation of Momentum
-
for collision system, the principle of conservation of momentum states that the total momentum b4 collision is equal to the totla momentum after collision, provided that no external forces acts on the system
-in elastic collision:
a) momentum is conserved
b) objects collide and bound apart
# m1u1+m2u2 = m1v1+m2v2
-in inelastic collision
a) momentum is conserved
b) objects collide and get attached to each other
# m1u1+m2u2 = (m1+m2)v

3 comments:

Mable said...

walao...dunno wat happened to my ticks...all same o =.=

尉语WY said...

38..n i wan kill u ...u post de comments...u wan die arhh!!!n chong dang me 2 reply my xue jie...wan die betul!!!><

Mable said...

huahaha...i only said 3 words...so jian dan de words...