The document discusses the principle of conservation of momentum. It defines conservation of momentum as the total momentum before collision or explosion being equal to the total momentum after. It provides examples of collisions where objects move separately or together after impact, as well as explosions where objects are in contact before but separate after. It then gives sample problems calculating momentum and velocity in situations involving colliding cars and trolleys.

2. Learning Objectives

4. The colliding objects move separately after collision.

5. m 1 m 1 m 2 u 1 u 2 v 1 v 2 Before collision After collision Momentum : m 1 u 1 + m 2 u 2 = m 1 v 1 + m 2 v 2 m 2

6. The colliding objects move together after collision.

7. m 1 m 2 m 1 + m 2 u 1 u 2 = 0 v Before collision After collision Momentum : m 1 u 1 + m 2 u 2 = (m 1 + m 2 ) v

8. The objects involved are in contact with each other before explosion and are separated after the explosion.

9. Before explosion After explosion (m 1 + m 2 ), u = 0 m 1 m 2 v 1 v 2 Momentum: (m 1 + m 2 )u = m 1 v 1 - m 2 v 2

12. QUIZ TIME!!

13. In the following figure, two particles of masses 1kg and 2kg are moving in the same direction at velocity of 30 ms -1 and 15 ms -1 respectively, If they stick together after collision, the final velocity of the particles is 30 ms -1 15 ms -1 1 kg 2 kg QUESTION 1 ANSWER : 20 ms -1

14. Two objects A and B of masses 2 kg and 1 kg respectively move in opposite directions. They collide head on. After the collision, the velocity of A becomes 1 m s -1 towards the left. What would be the velocity of B ? 2 ms -1 4 ms -1 A B QUESTION 2 ANSWER : 2 ms -1 (To the right)

15. A trolley of mass 1 kg travelling at 3 m s -1 collides with a stationary trolley of mass 2 kg. If the two trolleys remain together after collision, their combined velocity immediately after collision, is QUESTION 3 ANSWER : 1 ms -1

16. Trolley A towards a stationary trolley B ahead. After collision, it is found that trolley B moves at a velocity of 8 m s -1 . The final velocity of trolley A is QUESTION 4 ANSWER : 14 ms -1

17. QUESTION 5 After collision, both trolleys sticked together. The collision is called ANSWER : Inelastic collision

20. Rocket gains momentum in the up direction The hot gases gain momentum in the down direction