force and pressure chapter 11 class 8 ncert

1. FORCE

2. FORCE??

3. A FORCE IS A PUSH OR PULL
OF AN OBJECT.

4. • WE CANNOT SEE FORCE BUT CAN OBSERVE
ITS EFFECTS.
• "NEWTON" IS A UNIT OF FORCE.
• FOR A FORCE TO COME INTO PLAY THE
INTERACTION OF TWO OBJECTS IS
NECESSARY.
• THE STRENGTH OF FORCE IS EXPRESSED IN
MAGNITUDE.

5. EFFECTS OF FORCES:-
• CHANGE IN DIRECTION
• CHANGE IN SPEED
• CHANGE IN SHAPE
• IT MAKES AN OBJECT AT REST TO MOVE
• IT MAKES A MOVING OBJECT TO REST

6. FORCES
BALANCED UNBALA
NCED
AND
CONTACT NON-
CONTACT

7. BALANCED
FORCES:-
• SAME AMOUNT OF
FORCE IS APPLIED ON
BOTH SIDES OF AN
OBJECT , IN SUCH A
CASE AN OBJECT WILL
NOT BE MOVING.

8. • WHEN BALANCED FORCES ACT ON AN
OBJECT WHICH HAS UNIFORM MOTION,
THEN ITS SPEED NEITHER INCREASES
NOR DECREASES.

9. UNBALANCED
FORCES:-
• THE FORCES APPLIED ON
AN OBJECT ARE NOT EQUAL
IN MAGNITUDE
• WHEN UNBALANCED
FORCES ACT ON AN
OBJECT AT REST IT MOVES.

10. •WHEN UNBALANCED
FORCES ACT ON OBJECT
WHICH HAS UNIFORM
MOTION ITS SPEED
INCREASES

11. CONTACT FORCES:-
•WHEN TWO OBJECTS ARE IN CONTACT WITH EACH
OTHER AND FORCE IS APPLIED ON THEM, THEN IT
IS KNOWN AS CONTACT FORCES.
•EXAMPLES- MUSCULAR FORCE, FRICTION

13. NON-CONTACT
FORCES:-
• WHEN THERE IS NO CONTACT BETWEEN THE
OBJECTS BUT FORCE IS APPLIED ON THEM THEN
IT IS CALLED NON-CONTACT FORCES.
• EXAMPLES- MAGNETIC FORCE, GRAVITATIONAL
FORCE, ELECTROSTATIC FORCE

15. THANK YOU