8/2/2019 Chapter 2and 3 Final
1/22
DEFINITION
Kinematics:
Systematic study of motion using distance, speed, time and acceleration is called
kinematics
Distance:
It is the length of path (scalar quantity)
Speed:
It Is the time rate of change of distance
Displacement:
It is the change in position of a particle from initial position to final position
Position:
It is the location of a particle with respect to reference point (origin)
X1
X2
X1
X1
8/2/2019 Chapter 2and 3 Final
2/22
Particle:
It is the point object with infinitesimal size.
Scalar:
The scalar quantity has magnitude (numerical value) but no direction
Example: mass, time, distance (length), temperature.
Vector:
A vector quantity has both magnitude and direction
Example: velocity , acceleration ( , displacement .
Velocity:
It is the rate of change of displacement
Average velocity:
Ratio of change in displacement () to change in time () is called average velocity
Instantaneous Velocity:
Limiting value of the ratio
as time approaches zero is called instantaneous velocity
Time (sec)
Displacement(m)
It is time rate of change of displacement
8/2/2019 Chapter 2and 3 Final
3/22
Acceleration:
It is the time rate of change of velocity
Average Acceleration:
Ratio of change in velocity ( ) to change in time (
Instantaneous Acceleration:
Limiting value of the ratio
as the time ( approaches zero
Graph
The acceleration of freely falling bodies is constant i.e.
a = slope of V-t graph
8/2/2019 Chapter 2and 3 Final
4/22
Mohammad Akhtar Kamran Page 1
KINEMATIC EQUATIONS
For accelerated motion
Second Equation of Motion
8/2/2019 Chapter 2and 3 Final
5/22
Mohammad Akhtar Kamran Page 2
Motion with constant acceleration-Calculation of distance travelled in a given time
8/2/2019 Chapter 2and 3 Final
6/22
Mohammad Akhtar Kamran Page 3
QUIZ:
What is the density of earth?
Solution:Mass of earth:
Radius of Earth:
Volume of Earth:
Density:
OR
8/2/2019 Chapter 2and 3 Final
7/22
Mohammad Akhtar Kamran Page 4
GRAPHICAL REPRESENTATION OF MOTION
Graph between position and time
For freely falling body
When the ball is thrown upward, the height increases with time to a maximum and then
decreases to zero
Slope (V) is the time rate of change of height ()
0
5
10
15
20
25
30
35
0 1 2 3 4 5
Distance(Y-axis)VsTime(X-axis)
Xx1
Position
X7
X6
X5
X4
X3
X2
X1
Time -t
At top:
Slope (V) = 0
At the end of curve
Slope steep downward and
represents the maximumdownward velocity
At the start of curve
Slope steep upward and represents
maximum upward velocity
8/2/2019 Chapter 2and 3 Final
8/22
Mohammad Akhtar Kamran Page 5
Graph between Velocity and time
The acceleration of freely falling body is constant
0 2 4 6 8 time
25
20
15
10
05
0
Velocity ms-1
0 1 2 3 4 5 6 Time (sec)
25
20
15
10
05
0
Acceleration
m.sec2
Constant acceleration g=9.8m.s-2
It means that acceleration is not changing
8/2/2019 Chapter 2and 3 Final
9/22
Mohammad Akhtar Kamran Page 1
Example-1:
The speed of sound in air is about 1100ft/sec. if the lightning strikes 1-mile from you and
produces thunder, how long will it take for the sound to reach you?
Solution:
Example-2:
If a falling object increases its velocity from 40m/sec to 60m/sec in 2 seconds then?
a. What is the acceleration?b. What is the average velocity during the interval?c. How far will it travel during the time?
Solution:
a).
b).
8/2/2019 Chapter 2and 3 Final
10/22
Mohammad Akhtar Kamran Page 2
c).
Distance travelled (s)?
()
Example-3:
a. Convert 20ft to inches
b. Convert 20ft to meter
c. Convert 1 mile to meter
Solution:
a. ( )
b. ( )
8/2/2019 Chapter 2and 3 Final
11/22
Mohammad Akhtar Kamran Page 3
c.
( )
THE CAUSE OF MOTIONDO YOU KNOW?
Isaac Newton (1942-1727) formulated three basic laws of mechanics These laws explain the behavior of moving object Einsteins theory of light explains the behavior of objects moving with velocities
near speed of light
MAX Planks Quantum theory is used for the description of the motionmicroscopic particles of atom and nuclei.
8/2/2019 Chapter 2and 3 Final
12/22
Mohammad Akhtar Kamran Page 4
Newtons LawsNEWTONS FIRST LAW OF MOTION:
An object will remain at rest or in uniform motion in a straight line unless some net
external force acts upon it.
Newtons first law of motion is also called Law of Inertia
REST:
An object is at rest if it does not change its position with respect to surroundings
MOTION:
An object is in a state of motion, if it changes its position with respect to surroundings
Quiz:
At rest or motion, who can tell?
Newtons Second Law:
The acceleration of an object is directly proportional to the net external force exerted
upon it and inversely proportional to its mass
8/2/2019 Chapter 2and 3 Final
13/22
Mohammad Akhtar Kamran Page 5
Force (F):
It is an agency which tends to change the state of motion or rest of an object
Mass (m):Mass of an object is a measure of the amount of matter in it and is a measure of its
inertia
It does not change, in a state of motion
It is a scalar quantity
Inertia:It is a resistance to change the state of rest ot sate of motion.
Larger the mass, greater the inertia Smaller the mass, smaller the inertia
Example:
If a man exerts a force of 100 Newton on a crate of mass 5kilogram, initially at rest, in
the absence of friction, Find (a) acceleration (b) speed and distance after 3 seconds.
Solution:
a)
b)
()
8/2/2019 Chapter 2and 3 Final
14/22
Mohammad Akhtar Kamran Page 6
Newtons third Law of Motion
When one body exerts a force on a second body, the second body exerts an equal
but oppositely directed reaction force on the first body
For every action there is an equal and opposite reaction.
F=100N
8/2/2019 Chapter 2and 3 Final
15/22
Mohammad Akhtar Kamran Page 7
Its the Law!
F12 = - F21
Example:
If a 2Kg mass is acted upon by a force of 10N what is the acceleration? If it is initially at
rest, what will be its velocity after 3seconds?
Solution:
a.
b.
8/2/2019 Chapter 2and 3 Final
16/22
8/2/2019 Chapter 2and 3 Final
17/22
Mohammad Akhtar Kamran Page 2
Example:
Centripetal force keeps a car on a circular track
Centripetal force keeps the earth to move around the sun
In the absence of centripetal force, an object leaves the circular path and travel
in the straight line according to Newtons law
Centripetal force in term of angular velocity
Centrifugal force (center fleeing force)
Force required to keep an object moving, away from center of circle is called
centrifugal force.
This force is equal and opposite of centripetal force
Clinical Application of Circular Motion:
8/2/2019 Chapter 2and 3 Final
18/22
Mohammad Akhtar Kamran Page 3
Laboratory centrifuge separate material according to their densities. Heavier particle in centrifuge will move to the outside. Less force will be required
to keep them moving in a circle as radius is larger.
It is used in separating material of different densities. It can be used to measure densities Ultracentrifuges are important tools in microbiology research, its speed
It is used to separate different type of proteins from cellular material
Forces as Vectors
Forces (F=ma) is a vector quantity and has both magnitude (numerical value) and
direction
There are several forces acting in different directions on a single object
Net external force is the sum of all the forces acting on an object i.e. The vector sum of two 50pound forces directed in opposite direction is zero.
( ) When two forces act at right angles, the resultant forces can be obtained by using
Pythagorean Theorem
PerpendicularHypoteneous
Base
4
2
8/2/2019 Chapter 2and 3 Final
19/22
Mohammad Akhtar Kamran Page 4
The diagonal of a rectangle gives the direction of resultant force. The angle ( ) can bemeasured by protractor.
Knee flexion abduction force vector diagram
Resultant Force
1 2 3
8/2/2019 Chapter 2and 3 Final
20/22
Mohammad Akhtar Kamran Page 5
The force of gravityThe earth attracts all objects towards its center due to gravity
Newtons law of gravitation:
It states that every object attracts every other object with the gravitational force, whichis proportional to the product of their masses and inversely proportional to the square of
distance between them
***REPAIRED***
R= distance between centers of masses
G= proportionality constant= 11 22
r
Earth
Stone
F on earth
F on stone
8/2/2019 Chapter 2and 3 Final
21/22
Mohammad Akhtar Kamran Page 6
Weight:
The weight of an object is defined as the force of gravity acting upon it
Weight Density
It is the weight per unit volume
Specific Gravity:
Ratio of density of material to density of water
Earth
MOON
Earth
8/2/2019 Chapter 2and 3 Final
22/22
Mohammad Akhtar Kamran Page 7
Example-1: What is the weight of 10kilogram object?
Solution:
m = 10Kg W = mg
g = 9.8N/Kg W= 10Kg 9.8N/Kg = 98N
Example-2: If a person has a mass of 5slug, What is his weight?
Solution
m = 5slug IN = mg
g = 32 Pound/slug W = 5slug 32 Pound/slug = 160 Pounds
Example-3Volume of a 100 gram block of aluminum is 37cm3. What is the density of
aluminum block?
Solution
Clinical Application of Gravity
Due to the downward pull of gravity, all objects tends to move to the lowestpossible position
Gravity drainage is used to remove fluid from the lungs The gravitational force provides the pressure for administration of intravenous
fluid, transfusion and so on
The force of gravity has an effect upon the circulation of fluid Because of gravitational Pull, the pressure in the blood vessels of legs and feet is
higher than that in head and neck and people have edema of the feet and legs
due to standing for long time
The gravity effect can be seen in the veins of arms and hands if the arms are lefthanging for long period
The improve gravity drainage, post-operative patient are often placed in specialposition.
Brain surgery may be performed in sitting position to lessen the danger ofhemorrhage.
The head may be elevated after surgery for drainage of blood from the brain.
Top Related