A 4.0 kg circular disk slides in the x- direction on a frictionless horizontal surface with a speed of 5.0 m/s as shown in the adjacent Figure. It collides with an identical disk that is at rest before the collision. The collision is elastic. Disk 1 goes off at an 60 5.0 m/s angle of 60 with respect to the x-direction. Disk 2 g 30 goes off at an angle of 30 with respect to the x-direction. What best describes the speeds of the disks after the collision?

Solution :

Let kg

m/s

Let and are the speeds of the disk and  after the collision.

So applying conservation of momentum in the y-direction,

Therefore, the disk 2 have greater velocity and hence more kinetic energy after the collision.

Now applying conservation of momentum in the x-direction,

m/s

So,

          = 4.33 m/s

Therefore, speed of the disk 2 after collision is 4.33 m/s

1.   what is light?

light is an electromagnetic wave visible to the human eye. 

2. what is a reflection?

the rebounding of a light ray when it hits a mirror.

3. what is the incident ray?

contacts the surface of an object.

4. what is the reflected ray?

bounces off a reflective surface.

5. what is the normal ray?

perpendicular to the surface of a mirror.

6. what is the angle of incidence?

an angle formed by the incident ray and the normal.

7. what is the angle of reflection?

an angle formed by the reflected ray and the normal.

8. what is refraction?

(bending.)

9. what is a converging lens?

bring together light rays that pass through.

10. what is a diverging lens?

spreads out light passing through.

11. focal point?

the real point where the refracted rays meet when the incident rays run parallel.

i copy pasted btw from an website..