Force and Laws of Motion Class 9 PPT

 Page 1


Force and laws of 
motion
Page 2


Force and laws of 
motion
Force
• It is the force that enables us to do any work.
•
• To do anything, either we pull or push the object. 
Therefore, pull or push is called force.
•
• Example – to open a door, either we push or pull it. 
A drawer is pulled to open and pushed to close.
Page 3


Force and laws of 
motion
Force
• It is the force that enables us to do any work.
•
• To do anything, either we pull or push the object. 
Therefore, pull or push is called force.
•
• Example – to open a door, either we push or pull it. 
A drawer is pulled to open and pushed to close.
Effects of force:
• Force can make a stationary body in motion. For example a football can be set 
to move by kicking it, i.e. by applying a force.
•
• Force can stop a moving body – For example by applying brakes, a running 
cycle or a running vehicle can be stopped.
•
• Force can change the direction of a moving object. For example; By applying 
force, i.e. by moving handle the direction of a running bicycle can be changed. 
Similarly by moving steering the direction of a running vehicle is changed.
•
• Force can change the speed of a moving body – By accelerating, the speed of a 
running vehicle can be increased or by applying brakes the speed of a running 
vehicle can be decreased.
•
• Force can change the shape and size of an object. For example - – By 
hammering, a block of metal can be turned into a thin sheet. By hammering a 
stone can be broken into pieces.
Page 4


Force and laws of 
motion
Force
• It is the force that enables us to do any work.
•
• To do anything, either we pull or push the object. 
Therefore, pull or push is called force.
•
• Example – to open a door, either we push or pull it. 
A drawer is pulled to open and pushed to close.
Effects of force:
• Force can make a stationary body in motion. For example a football can be set 
to move by kicking it, i.e. by applying a force.
•
• Force can stop a moving body – For example by applying brakes, a running 
cycle or a running vehicle can be stopped.
•
• Force can change the direction of a moving object. For example; By applying 
force, i.e. by moving handle the direction of a running bicycle can be changed. 
Similarly by moving steering the direction of a running vehicle is changed.
•
• Force can change the speed of a moving body – By accelerating, the speed of a 
running vehicle can be increased or by applying brakes the speed of a running 
vehicle can be decreased.
•
• Force can change the shape and size of an object. For example - – By 
hammering, a block of metal can be turned into a thin sheet. By hammering a 
stone can be broken into pieces.
Types of force:
• There are two types of force
• * Balanced force
• *  Unbalanced force
Page 5


Force and laws of 
motion
Force
• It is the force that enables us to do any work.
•
• To do anything, either we pull or push the object. 
Therefore, pull or push is called force.
•
• Example – to open a door, either we push or pull it. 
A drawer is pulled to open and pushed to close.
Effects of force:
• Force can make a stationary body in motion. For example a football can be set 
to move by kicking it, i.e. by applying a force.
•
• Force can stop a moving body – For example by applying brakes, a running 
cycle or a running vehicle can be stopped.
•
• Force can change the direction of a moving object. For example; By applying 
force, i.e. by moving handle the direction of a running bicycle can be changed. 
Similarly by moving steering the direction of a running vehicle is changed.
•
• Force can change the speed of a moving body – By accelerating, the speed of a 
running vehicle can be increased or by applying brakes the speed of a running 
vehicle can be decreased.
•
• Force can change the shape and size of an object. For example - – By 
hammering, a block of metal can be turned into a thin sheet. By hammering a 
stone can be broken into pieces.
Types of force:
• There are two types of force
• * Balanced force
• *  Unbalanced force
Balanced force:
If the resultant of applied forces is equal to zero, it is called balanced forces.
Example : - In the tug of war if both the teams apply similar magnitude of 
forces in oppoisite directions, rope does not move in either side. This happens 
becasue of balanced forces in which resultant of applied forces become zero.
Balanced forces do not cause any change of state of an object. Balanced forces 
are equal in magnitude and opposite in direction.
Balanced forces can change the shape and size of an object. For example -
When forces are applied from both sides over a balloon, the size and shape of 
balloon is changed.