FORCES AND LAWS OF MOTION

FORCEForce is a push or pull applied to an object resulting from the objects interaction

with another object.

DIRECTION OF FORCE

The direction in which a body is

pushed or pulled.

RESULTANT FORCE

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

BALANCED AND UNBALANCED FORCE

BALANCED FORCE

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

UNBALANCED FORCEThe 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

Some Examples 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.

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

Newton’s Laws of Motion

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.

FIRST LAW OF MOTION

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.

INERTIAThe 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).

CLASSIFICATION OF INERTIA

Inertia of restInertia of motion

Inertia of direction

Example of Inertia

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.

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).

SECOND LAW OF MOTION

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.

MOMENTUM 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”

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.

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.

THIRD LAW OF MOTIONFor 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.

MADE BY:- PATIL RAKSHACLASS:- 9th ROSESUB:- PHYSICS