Download The Third Law of Motion Momentum

rd
3
Newton’s
Law of Motion:
Momentum
Section 3: The Third Law of Motion
Objectives:
• State Newton’s third law of motion.
• Identify action and reaction forces.
• Calculate momentum.
• Recognize when momentum is conserved.
Third Law of Motion
• The third law states that for every action
(force) in nature, there is an equal and
opposite reaction.
• For example, if object A exerts a force on
object B, then object B also exerts an equal
and opposite force on object A.
• The forces are exerted on different objects.
Newton’s 3rd Law of Motion (cont.)
Examples:
– Swimming- arms push
against water, water pushes
swimmer ahead
– Rocket Propulsion- hot gases
produced by burning fuel are
pushed out of the engine’s
nozzle, pushing the rocket or
car ahead
Momentum:
•
Related to the amount of force that is needed to
change the motion of a moving object.
Which is more difficult to stop…
a semi-truck or VW Beetle?
*** depends on velocity and mass
•
•
Increase in mass or velocity results in an increase
in momentum.
Law of Conservation of Momentum: The total
amount of momentum in a system is conserved.
Momentum Sports Example
• Football linemen- hard to start moving, hard
to stop moving!
Momentum:
Equation: Momentum = Mass x Velocity
SI Units: kg x m/s (and direction)
p = mv
Momentum Problem
What is the momentum of a 10.0 kg bowling
ball moving down a bowling alley at 6.0 m/s?
Known: m = 10.0 kg
v = 6.0 m/s
Unknown: p = ___kg x m/s
Formula: p = mv
p = 10.0 kg x 6.0 m/s = 60 kg x m/s