Download Newton`s Third Law and Momentum

Newton’s Third Law and
Momentum
Newton’s Third Law
According to Newton’s third law of motion,
whenever one object exerts a force on a
second object, the second object exerts an
equal and opposite force on the first object
Newton’s Third Law cont.
“For every action, there is an equal and
opposite reaction”
Action and Reaction Forces
The action force is the force that has motion
The reaction force is the force that reacts to the
motion
Action and Reaction cont.
Example: When hanging a picture, you use a
hammer to drive a nail into the wall.
The hammer strikes the nail, it applies a force to
the nail (action)
The nail also applies an equal and opposite force
to the hammer (reaction force)
Action and Reaction Forces Cont.
Not all action and reaction forces result in
motion
Simply pushing against a wall creates action and
reaction forces
Momentum
Momentum is the product of an
object’s mass and its velocity
Momentum cont.
Objects with large momentums are harder to
stop than objects with little momentum
Example: it is harder to stop a moving car than
to stop a person walking
Momentum cont.
An object has a large momentum if its velocity is
large and it has a large mass
An object has a small momentum if its velocity is
small and it has a small mass
Momentum cont.
Calculating Momentum
To calculate momentum you multiply an object’s
mass and its velocity
Momentum = Mass x Velocity
Calculating Momentum
Example: A bowling ball weighs 7kg and has a
speed of 6 meters per second
Momentum = 7kg x 6 m/s
Momentum = 42 kg(m/s)
Conservation of Momentum
In a closed system, the loss of momentum of
one object equals the gain in momentum of
another object
Conservation of Momentum
Conservation of Momentum
What are we doing?
1) Momentum Worksheet (Due end of hour)
1) Vocabulary (Due Monday)
1) Answer the “Assessment” questions on pg
377
1) Read ahead: Universal Forces pg 378-382