Lecture 2

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Published on 11 Dec 2010
PHY1012- Lec. 2
Quantifying Motion
introducing quantities such as speed and velocity to help us better
understand motion
Speed = change in position
change in time
velocity = speed & direction objects move
Acceleration = change in velocity
change in time
velocity has km/s and direction
so acceleration also has km/s2 and direction
momentum = mass of object x velocity of object
force = push or pull
suppose there is a system if objects and he total force on the system is zero
(velocity is zero)
The total momentum of the system is the sum of the individual momentum
of each object
the total momentum of the system is a conserved quantity. It stays the
same at all time
This is called Conservation of Momentum
Q= According to the above, can we observe one ball come in mv and 2 balls
exit with ½ mv?
m= mass of one ball v = speed of incident ball
Total initial momentum of system: mv + 0 + 0 + 0 + 0 = mv
other balls have zero momentum
because not moving
Total final momentum of system
0 + 0 + 0 + ½ mv + ½ mv = mv*
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