Download THE LAWS OF MOTION

THE LAWS OF MOTION
A Presentation
By
Mrs. Pooja P.Dani
Overview
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Force and Motion
Balanced and Unbalanced Forces
Types of inertia
Newton’s First Law of Motion
Newton’s Second Law of Motion
Newton’s Third Law of Motion
Principle Conservation of Momentum
Force and Motion
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The force is required to put a stationary body in motion or to stop a moving
body.
The force can be used to change the velocity of an object or direction of
motion.
The force can also change the shape of the body.
When a we push, pull or heat an object we make a force to act on them,
due to which we can bring the object in motion or can stop it.
Force is a physical quantity that changes or tends to change the state of
rest or of uniform motion of a body in a straight line.
For Example:
You might have seen a car in motion. We can stop the car by applying
brakes which is nothing but a force applied on the car
Balanced and Unbalanced Forces
If the forces on an object are equal and opposite, they are
said to be balanced, and the object experiences no change in
motion. If they are not equal and opposite, then the forces
are unbalanced and the motion of the object changes
Balanced and Unbalanced Forces
A soccer ball is sitting at
rest. It takes an
unbalanced force of a
kick to change its motion.
Two teams are playing tug of war. They are both
exerting equal force on the rope in opposite
directions. This balanced force results in no
change of motion.
Inertia
Inertia: the tendency of an object to resist changes in
its state of motion
Real Life example:
We can explain the term inertia with the following
example. Suppose we are traveling in a bus, and
the bus suddenly starts moving we experience a
jerk. When the bus is at rest our body is also at
rest and as the bus starts its motion, the portion of
the body which is in contact with the bus acquires
velocity but the upper part of the body tries to
remain at rest. So we fall back!
The exact opposite situation occurs when moving
vehicle suddenly stops by application of brakes.
Types of Inertia
• Inertia at Rest
The inherent property of
a body by virtue of
which it can not
change its position of
rest, is called inertia
of rest.
Types of Inertia
• Inertia of motion
The inherent property of
a body by virtue of
which it can not
change its state of
motion, is called
inertia of motion.
Types of Inertia
• Inertia of Direction
The inherent property of a body by virtue of which it can not
change its direction of motion, is called inertia of direction
Below is a video which demonstrates the process of sharpening a knife
and how sparks fly off tangentially during this process.
http://www.ehow.com/video_4418693_sharpening-spade-drill-bit.html
Background
Sir Isaac Newton (1643-1727) an
English scientist and
mathematician famous for his
discovery of the law of gravity
also discovered the three laws of
motion. He published them in his
book Philosophiae Naturalis
Principia Mathematica
(mathematic principles of
natural philosophy) in 1687.
Today these laws are known as
Newton’s Laws of Motion and
describe the motion of all objects
on the scale we experience in
our everyday lives.
Newton’s First Law of Motion
http://www.youtube.com/watch?v=iDGvBWmUcFU&feature=related
In this video you can see the glass is placed on the
paper. When we pull the paper at once, the glass
remains steady on the table. This proves Newton’s
First Law of motion.
It states that…
“Every inanimate body continues in its state of rest
or of uniform motion in a straight line unless an
external unbalanced force acts on it.”
The first law is also called as Law of Inertia.
Newton’s Second Law of Motion
http://zonalandeducation.com/mstm/physics/mechanics/forces/newton/ne
wtonLaw2.html
It states that…
“The rate of change of momentum is directly
proportional to the impressed force and takes place
in the direction in which the force acts.”
Newton’s Second Law of Motion
• If a body of mass m moving with velocity u be subjected to force F
acting in the direction of motion.
• Suppose v is the velocity of body after time t.
• The total initial momentum of body is mu and final momentum is mv
after time t.
• Hence
rate of change of momentum = change in momentum/time
=(mv-mu)/t
=m(v-u)/t
=ma
Hence rate of change of momentum is α F
ma α F
Newton’s Third Law of Motion
As you can see in this picture
the rocket is being launched.
Various fuels are burned in the
engine, producing hot gases.
The hot gases push against the
inside tube of the rocket and
escape out the bottom of the
tube. As the gases move
downward, the rocket moves in
the opposite direction.
This is the demonstration of Newton’s
Third law of motion.
Newton’s Third Law of Motion
“To every action there is an equal
and opposite and instantaneous
reaction”
Action and reactions are the terms
explaining force.
Principle of conservation of
momentum
Just click the link given below. This is a small
demo of principle of conservation of momentum.
http://www.physicsclassroom.com/mmedia/momentum/cbb.cfm
The principle of conservation of momentum states that –
“If there is no net force acting on two interacting bodies
then there total momentum is conserved.”
In other word
“If two freely moving bodies collide their total momentum
after collision is the same as their total momentum
before collision.”
Check Your Understanding
• 1. What acceleration will result when a 12 N net force
applied to a 3 kg object?
• 2. A net force of 16 N causes a mass to accelerate at a
rate of 5 m/s2. Determine the mass.
• 3. How much force is needed to accelerate a 66 kg skier
1 m/sec/sec?
• 4. What is the force on a 1000 kg elevator that is falling
freely at 9.8 m/sec/sec?
Thank You