Pool Billiard can be viewed as elastic collision in 1D if balls are hit head on. Professional tables have balls of equal mass. What happens if the white ball hits the 8 ball head on (ignore friction)?

1
Pool Billiard can be viewed as elastic collision
in 1D if balls are hit head on. Professional
tables have balls of equal mass. What happens if
the white ball hits the 8 ball head on (ignore
friction)?

• White ball slows down, both balls move after
  collision
• White ball stops, 8 ball moves with white balls
  velocity
• White bounced back ( neg. velocity), 8 ball moves
  forward slowly
• White ball stops, 8 ball moves forward with less
  than white balls velocity

2
Pool Billiard can be viewed as elastic collision
in 1D if balls are hit head on. Bar tables have a
heavier white ball. What happens if the white
ball hits the 8 ball head on (ignore friction)?

• White ball slows down, both balls move after
  collision
• White ball stops, 8 ball moves with white balls
  velocity
• White bounced back ( neg. velocity), 8 ball moves
  forward slowly
• White ball stops, 8 ball moves forward with less
  than white balls velocity

3
Collision Problem Solving

• Choose your system
• Is momentum conserved, i.e. are only internal
  forces acting on the systems constituents?
• Draw two diagrams initial and final situation
• Choose a coordinate system, in particular and
  directions
• Apply monetum conservation equations
• If elastic collision apply kinetic energy
  conservation equation
• Solve for unknowns
• Check results (reasonable?)

4
Example Inelastic collision

• Two balls of clay with velocities v1 and v2
  collide. After collision they are stuck together,
  what is their velocity?

5
Example Elastic collision

• A white billiard ball of 100g and v2m/s collides
  head-on with the 8-ball of 90g at rest.
• What are the velocities of the balls right after
  the collision?

6
Example Collision in 2D

• Neutron hits Helium target elastically with v6.2
  105 m/s and Helium off at an angle of 45
  degrees.
• What are the velocities (vectors!) of the protons
  after the collision?

7
A ladybug sits at the outer edge of a
merry-go-round, and a gentleman bug sits halfway
between her and the axis of rotation. The
merry-go-round makes a complete revolution once
each second. The gentleman bugs angular speed is

• half the ladybugs.
• the same as the ladybugs.
• twice the ladybugs.
• impossible to determine.

8
A ladybug sits at the outer edge of a
merry-go-round, that is turning and slowing down.
The vector representing her angular velocity is
in the

• -z direction
• z direction
• y direction
• zero

z
y
x
9
A ladybug sits at the outer edge of a
merry-go-round, that is turning and slowing down.
At the instant shown, the radial component of the
bugs (Cartesian) acceleration is in the

• -x direction
• y direction
• z direction
• Zero

z
y
x
10
A ladybug sits at the outer edge of a
merry-go-round, that is turning and slowing down.
At the instant shown, the bugs angular
acceleration is in the

• -z direction
• -y direction
• y direction
• z direction

z
y
x
11
A ladybug sits at the outer edge of a
merry-go-round, that is turning and slowing down
due to a force exerted on its edge. At the
instant shown, the torque on the disc is pointing
in

• -z direction
• -y direction
• y direction
• z direction

z
y
F
x
12
A ladybug sits at the outer edge of a
merry-go-round, that is turning and slowing down
due to a force exerted on its edge. The angular
momentum of the bug is pointing in

• -z direction
• -y direction
• y direction
• z direction

z
y
F
x
13
What is A x A ?

• Zero
• A
• -A
• A2