CLASS 9 CONTENT laws of motion physics

1. FORCES AND LAWS OF MOTION

2. Force is a push or pull
applied to an object
resulting from the objects
interaction with another
object.

4. The direction in which a
body is pushed or
pulled.

5. The resultant force is that signal
force which when acting on a
body produces the same effect
as that produced by a number of
forces

7. Force which do not cause any change in state
rest or of uniform motion along a straight line
are called balanced force.
The resultant of
balanced force is always equal to zero

9. The force acting on a body
produce any change in state of rest
or motion, then the force is said to
be unbalanced force.
The resultant of unbalanced force
is always greater than zero

10. 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.
A soccer ball is sitting at rest. It takes
an unbalanced force of a kick to
change its motion.

12. 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.

13. A body at rest or in motion
at a constant speed along a
straight line remains in that
state of rest or motion
unless acted upon by an
outside force.

14. The tendency of an object
to resist any change in its
state of rest or uniform
motion is called INERTIA
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).

15. Inertia of rest
Inertia of motion
Inertia of direction

16. Because of inertia, objects (including you) resist changes in
their motion. When the car going 80 km/hour is stopped
by the brick wall, your body keeps moving at 80 m/hour.

17. 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).

18. States that the rate of change of
momentum is directly proportional
to applied force and take place in the
same direction as the applied force.

19. The momentum of an
object is define as the
product of its mass and its
velocity
The momentum is
a vector quantity and is
represented by “p”

20. Newton’s 2nd Law proves that different
masses accelerate to the earth at the same
rate, but with different forces.
We know that objects
with different masses
accelerate to the ground
at the same rate.
However, because of
the 2nd Law we know
that they don’t hit the
ground with the same
force.

21. What does F = ma say?
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.

22. 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.