MSTC Physics 2

1
MSTC Physics 2

• Chapter 6
• Sections 3 and 4

2
3 types of collisions

• Elastic collisions
• Inelastic collisions
• Completely inelastic collisions
• Regardless of the type of collision, momentum is
  conserved.

3
completely elastic collision

• Collision in which no kinetic energy is lost
• (In the real world there is no such thing but we
  do get close.)
• Example 2 billiard balls

4
Inelastic collision

• Collision in which some kinetic energy is lost
• Example all real world collisions like a car
  crash

5
Completely inelastic collision

• Collision in which 2 objects stick together
  during the collision and a great deal of kinetic
  energy is lost
• Example ballistic pendulum, 2 train cars that
  couple on the track

6
Completely elastic collision

• V1f (m1 m2) v1 (2m2) v2
• (m1 m2) (m1 m2)
• V2f __(2m1)_ v1 - (m1 m2) v2
• (m1 m2) (m1 m2)

7
Sample Problem

• 1. Consider the completely elastic collision
  between masses of 100 g and 200 g. The first
  mass is moving with a velocity of 30 cm/s to the
  right and the second mass has a velocity of 20
  cm/s to the right. Find the final velocities of
  the two balls.

8
Sample Problem

• 2. Consider the completely elastic collision
  between 2 balls of masses 100 g and 200 g, with
  velocities of 20 cm/s to the right and 30 cm/s to
  the left respectively. Find the final velocities
  of the two balls.

9
Sample Problem

• 3. A ball of mass 0.25 kg and velocity 5 m/s
  collides head-on with a ball of mass 0.8 kg that
  is initially at rest. If the collision is
  elastic, what are the velocities of the balls
  after the collision?

10
Sample Problem

• 4. A 50 g piece of clay moving at a velocity of
  5 cm/s to the right has a head-on collision with
  a 100 g piece of clay moving at a velocity of 10
  cm/s to the left. The two pieces of clay stick
  together during the impact. Find the final
  velocity of the clay, the initial kinetic energy,
  the final kinetic energy, and the amount of
  energy lost in the collisiion.

11
Sample Problem

• 5. Two cars collide at an intersection. Car 1
  has a mass of 1200 kg and is moving at a velocity
  of 95 km/h due east. Car 2 has a mass of 1400 kg
  and is moving at a velocity of 100 km/h due
  north. The cars stick together and move off at
  an angle. Find the final velocity of the
  combined cars.

12
Sample Problem

• 6. Billiard ball 2 is at rest when it hits with
  a glancing collision by ball 1 moving at a
  velocity of 50 cm/s toward the right. After the
  collision ball 1 moves off at an angle of 35
  degrees from the original direction while ball 2
  moves at an angle of 40 degrees. The mass of
  each billiard ball is 0.017 kg. Find the final
  velocity of each ball after the collision.