Newton laws of motion

1. Newton’s Laws of
Motion

2. Guided By:-
Vineet Sir

3. 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.
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.

4. “ -Sir Isaac Newton

5. Newton’s Laws of Motion
1. An object in motion tends to stay in motion and an
object at rest tends to stay at rest unless acted upon
by an unbalanced force.
2. Force equals mass times acceleration
(F = ma).
3. For every action there is an equal and opposite
reaction.

6. Newton’s First Law
An object at rest tends to stay at
rest and an object in motion tends
to stay in motion unless acted
upon by an unbalanced force.

7. Newton’s First Law is also called the
Law of Inertia
Inertia: The tendency of an object to resist
changes in its state of motion
The First Law states that all objects have
inertia. The more mass an object has, the
more inertia it has (and the harder it is to
change its motion).

8. Example from Real Life
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.

9. A powerful locomotive begins to pull a
long line of boxcars that were sitting at
rest. Since the boxcars are so massive,
they have a great deal of inertia and it
takes a large force to change their
motion. Once they are moving, it takes
a large force to stop them.
On your way to school, a bug
flies into your windshield. Since
the bug is so small, it has very
little inertia and exerts a very
small force on your car (so small
that you don’t even feel it).

10. If objects in motion tend to stay in motion,
why don’t moving objects keep moving
forever?
Things don’t keep moving forever because
there’s almost always an unbalanced force
acting upon it.
A book sliding across a table slows
down and stops because of the force
of friction.
If you throw a ball upwards it will
eventually slow down and fall
because of the force of gravity.

11. Newton’s Second Law
Force equals mass times acceleration.
F = ma
Acceleration: a measurement of how quickly an
object is changing speed.

12. What does F = ma mean?
Force is directly proportional to mass and acceleration.
Imagine a ball of a certain mass moving at a certain
acceleration. This ball has a certain force.
Now imagine we make the ball twice as big (double the
mass) but keep the acceleration constant. F = ma says
that this new ball has twice the force of the old ball.
Now imagine the original ball moving at twice the
original acceleration. F = ma says that the ball will
again have twice the force of the ball at the original
acceleration.

13. Examples
F = ma basically means that the force of an object
comes from its mass and its acceleration.
Something very small (low mass) that’s
changing speed very quickly (high
acceleration), like a bullet, can still
have a great force. Something very
small changing speed very slowly will
have a very weak force.
Something very massive (high mass)
that’s changing speed very slowly (low
acceleration), like a glacier, can still
have great force.

14. Accelerationisproducedwhenaforceactsona
mass. Thegreaterthemass(oftheobjectbeing
accelerated)thegreatertheamountofforceneeded
(toacceleratetheobject).

16. Mike's car, which weighs 1,000
kg, is out of gas. Mike is trying
to push the car to a gas station,
and he makes the car go 0.05
m/s/s. Using Newton's Second
Law, you can compute how much
force Mike is applying to the
car.
F=1000×0.05
=50 newton

17. Newton’s Third Law
For every action there is an equal and
opposite reaction.

18. What does this mean?
For every force acting on an object, there is an equal
force acting in the opposite direction. Right now,
gravity is pulling you down in your seat, but Newton’s
Third Law says your seat is pushing up against you
with equal force. This is why you are not moving.
There is a balanced force acting on you– gravity
pulling down, your seat pushing up.

19. To walk on the ground we push the ground
backwards with our foot, as a reaction, the
ground pushes our foot forward with the
same force. It is this forward reaction force
of the ground that enables us to walk
forward.

20. This means that for every force there is a reaction
force that is equal in size, but opposite in direction.
That is to say that whenever an object pushes
another object it gets pushed back in the opposite
direction equally hard.
The rocket's action is to push down on the ground
with the force of its powerful engines, and
the reaction is that the ground pushes the rocket
upwards with an equal force.

21. While trying to sWim a sWimmer
pushes the Water backWards With
his hands and feet. this is the force
of action. the Water pushes the
sWimmer forWard With the same
force (of reaction)

22. When abullet isfired from agun, thegun recoilsthe
gun movesbackwardsthrough asmall distancegiving
jerk to theshoulder of thegunman. Thisisbecauseon
firing , thegun exertssomeforceon thebullet in
forward direction. In turn, thebullet exertsan equal
forceon thegun in thebackward direction. Thedistance
moved by thegun issmall becausegun ismuch heavier
than thebullet.

23. rest near a river bank. As the
sailor jumps from the boat to
the river bank, the boat is
pushed away from the bank.
This happens due to equal
forces of action and reaction.

24. Law of conservation

25. Conservation laws are fundamental to our understanding of the physical world, in
that they describe which processes can or cannot occur in nature. For example,
the conservation law of energy states that the total quantity of energy in an
isolated system does not change, though it may change form. In general, the total
quantity of the property governed by that law remains unchanged during physical
processes. With respect to classical physics, conservation laws include
conservation of energy, mass (or matter), linear momentum, angular momentum,
and electric charge. With respect to particle physics, particles cannot be created or
destroyed except in pairs, where one is ordinary and the other is an antiparticle.
With respect to symmetries and invariance principles, three special conservation
laws have been described, associated with inversion or reversal of space, time,
and charge.
Conservation laws are considered to be fundamental laws of nature, with broad
application in physics, as well as in other fields such as chemistry, biology,
geology, and engineering.
Most conservation laws are exact, or absolute, in the sense that they apply to all
possible processes. Some conservation laws are partial, in that they hold for some
processes but not for others.

26. Thank You
Aashutosh Agrawal
Class-IX
Sec-B