2. Two-Dimensional Collisions

3. Outcomes
You will explain, quantitatively, that momentum is conserved in one- and two- dimensional interactions in an isolated system

4. Law of Conservation of Momentum
Momentum is ALWAYS conserved during collisions
In 2-dimensional collisions we must consider momentum in each plane
Meaning: where no external net force acts on the system, the momentum of the system in both the ‘x’ & ‘y’ directions remains constant
The vector sum of the momenta is constant
So, 𝑝 𝐵𝑦 = 𝑝 𝐴𝑦 & 𝑝 𝐵𝑥 = 𝑝 𝐴𝑥

5. Explosions
When an explosion occurs, the vector sum of the momenta is zero, since prior to the explosion the sum of the momenta is zero.
When solving 2D problems…. USE TRIGONOMETRY & DRAW A DIAGRAM!!!

6. Sample Problem:
A 4.0 kg object is traveling south at a velocity of 2.8 m/s when it collides with a kg object traveling east at a velocity of 3.0 m/s. If these two objects stick together upon collision, at what velocity do the combined masses move?
(2.1 m/s at 58.1º E of S)

7. Homework
p. 11 #1-3

9. (Day#2)Sample Problem:
A curling rock, with a mass of 10.0 kg, moves to the right at 2.50 m/s towards a stationary rock with a mass of 12.5 kg. After the collision, the 12.5 kg rock moves off at an angle of 60.0 from the original motion of the 10.0 kg rock at a speed of m/s. Calculate the velocity of the first rock after the collision.
(2.2 m/s at 30º)

10. Sample Problem:
A 4.0 kg object is moving east at an unknown velocity when it collides with a kg stationary object. After the collision, the 4.0 kg object is traveling at a velocity of 2.8 m/s 32º N of E and the 6.1 kg object is traveling at a velocity of 1.5 m/s 41º S of E. What was the velocity of the 4.0 kg object before collision?
(4.1 m/s East)

11. (Day)Sample Problem:
A stationary 4.0 kg object burst into 3 fragments. The 1.5 kg piece flies off to the west at 1.8 x 102 m/s while the 2.1 kg piece flies off north at 2.1 x 102 m/s. What is the velocity of the third piece?
(1.3x103 m/s at 31º E of S)

12. Homework
p. 11 #4-6
p. 499 #1-4 (read p. 498) - Extra

13. Homework
p. 14 & 15 Diploma Q’s
2D collision WS
2D Quiz Tomorrow!