Transcript Collisions

Newtons 3rd Law:
For every force (action), there is an equal and
opposite force (reaction).
ACTION
A hammer applies a force to a
nail.
Rocket applies a force to gas
molecules.
Boxing glove applies a force to a
chin.
The Earth applies a force on a
falling apple.
Your feet apply a force on the
floor as you walk.
A book applies a force on a
table.
REACTION
The nail applies a force to the
hammer
The gas molecules apply a force to
the rocket
The chin applies a force to the glove
The apple applies a force to the
Earth
The floor applies a force to your feet
The table applies a force to the book
Newton’s 3rd Law Video
Collisions
Objective: TSW apply conservation of
momentum by calculating the velocities of
two objects before and after collisions.
m1
v1
v2
m1
?
m1
m2
m2
?
m2
F12
F21
m1
F12 =
m2
-F21
Conservation of Momentum
 po   p f
m1v1o  m2 v2o  m1v1 f  m2 v2 f
inelastic:
Momentum is conserved, Kinetic energy is not.
The objects are deformed.
5m/s
2kg
3m/s
2m/s
4kg
??
2kg
4kg
perfectly inelastic: Momentum is conserved, Kinetic energy is not.
Objects are deformed and they stick together.
5m/s
2m/s
2kg
??
2kg
3kg
3kg
perfectly inelastic:
4m/s
4m/s
2kg
??
2kg
2kg
2kg
inelastic
v=0
2kg
5m/s
3kg
??
2kg
3kg
elastic:
Momentum and Kinetic energy are both conserved.
Objects collide without touching. Only occurs at the
molecular level, billiard balls are close.
3m/s
5kg
0m/s
5kg
??
??
5kg
5kg
If the masses are the same they swap
velocities.
elastic
3m/s
5kg
6m/s
5kg
??
??
5kg
5kg
elastic
6m/s
4kg
4m/s
2kg
??
??
4kg
2kg