Chapter one: lesson one
Concept of motion.
Motion : Is the change of the position of an object
relative to a fixed point as time passes.
- Object classification according to motion:
Object
Object doesn't
change its position
relative to fixed
point as time passes
Object change its
position relative to
fixed point as time
passes
- Types of motion: -
Is the motion that
has starting point
and ending point
Is the motion that
repeates itself over
same period of time
1- Sreaight line
motion.
1- Circular motion
2- Vibrational motion
2- Projectiles motion
3- Wave motion
- The simplest type of motion is the straight-line motion as train
motion and transportation motion.
- To describe the motion of an object, it must to realize some
physical concepts:
1. Time (Fundamental, scalar){ Discussed before}
2. Displacement (Fundamental, Vector){Discussed unit 1, chapter 2}
3. Velocity (Derived, Vector)
4. Acceleration (Derived, Vector)
3. Velocity Is the rate of change o displacement.
ν=
𝛥𝑑
𝛥𝑡
=
𝑑2−𝑑1
𝑡2−𝑡1
Is the displacement moved by an object in one second.
- Measuring units: m/sec, km/h
m/sec
-1
- Dimensional formula: L . T
km/h
5/18
- What is the difference between speed and velocity?
speed
Velocity
It is the distance moved by the object It is the displacement of the object
per unit time
per unit time
(scalar, Vector)
(Derived, Vector)
Always positive
Maybe negative or positive according
to direction of motion.
Ex: a car moves at speed 90 km/h
Ex: a car moves at velocity 80 km/h
towards east
- Types of velocity:-
Uniform velocity
It is the Velocity in which the
object moves through equal
displacements in equal intervals of
time
Non-uniform velocity
It is the velocity in which the object
moves through unequal
displacements in equal intervals of
time
Velocity of object remains constant Velocity may change its magnitude
.
and direction.
Instantaneous velocity
It is the velocity of the object at a
given instant
Average velocity
It is given by dividing the total
displacement of the object from the
starting point to the end point by the
total time of motion
Example(1): A person drove a car in a straight line to cover 8.4 km in 0.12 h. because
the fuel had run out, he walked through 2 km along the same straight line to reach the
nearest gas station after 0.5 h. calculate the average velocity of this journey.
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Example(2): If the person in the previous example returned back to his car in 0.6 h ,
find the average Velocity during the whole story.
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Example(3):the next graph represents the motion of a girl from her home till
returning back . study the. Diagram then mention
a. The point at which the girl has stopped.
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b. The maximum velocity at which the girl has moved.
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c. Why is the velocity negative when returning back?
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d. The difference between the displacement and the distance moved by
the girl .
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