Transcript Ch 5- Momentum

CH 5MOMENTUM
BIG IDEA: THE
FORCE ACTING ON
AN OBJECT
M U LT I P L I E D B Y T H E
T I M E T H AT F O R C E
ACTS EQUALS THE
OBJECTS CHANGE IN
MOMENTUM
5.1 MOMENTUM IS INERTIA IN MOTION
Momentum= mass X velocity
(momentum = mv)
The more momentum something has, the
more difficult it is to stop and the larger
effect it will have in a collision
5.2 IMPULSE CHANGES MOMENTUM
Force and the amount of time a force is being exerted produce
acceleration
If you exert the same force over a longer period of time, a greater
change in momentum results
Impulse- the quantity force times the time interval
Impulse-momentum relationship: The greater the impulse exerted
on something, the greater the change in momentum.
Impulse= change in momentum
OR Ft= change in mv
5.3 INCREASING MOMENTUM- INCREASE
FORCE, TIME, OR BOTH
Greatest momentum= greatest
force over longest period of time
5.4 PRACTICAL USES OF THE IMPULSEMOMENTUM RELATIONSHIP
If you are in a fast moving vehicle and the brakes
fail would you rather be forced to a stop by a wall or
by a haystack?
The haystack has a softer impact
-Either way the momentum decreases by the same
amount in coming to rest.
By hitting the haystack instead of the wall, you
extend the contact time- the time during which
momentum is brought to zero.
THE IMPULSE-MOMENTUM
RELATIONSHIP IN SPORTS
Think about:
Force-time-momentum relationship for:
Boxers punching, tennis players hitting,
Cushioned tennis shows/ mats, etc.
5.5 MOMENTUM IS CONSERVED
WHEN NO EXTERNAL FORCE ACTS
Internal forces don’t affect momentum
To change momentum and outside force is
required
Law of conservation of momentum: In the
absence of an external force, the momentum of
a system remains unchanged.
5.6 MOMENTUM IS CONSERVED IN
COLLISIONS
In any collision we can say:
Net momentumbefore collision = net momentumafter collision
Elastic collision:when
objects collide w/out
being permanently
deformed and w/out
generating heat
Inelastic collision- whenever colliding objects
become tangled or coupled together
By looking at the figure below we can see
that the v is 5m/s.
Twice as much mass
moves after the
collision, with half as
much velocity as
before the collision.