Impulse and Momentum AP Physics.
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Transcript of Impulse and Momentum AP Physics.
Impulse and Momentum AP Physics Impulse = Momentum Momentum is
defined as Inertia in Motion Ns
Consider Newtons 2nd Lawand the definition ofacceleration Units of
Impulse: Units of Momentum: Ns Kg m/s Momentum is defined asInertia
in Motion Example Momentum, Impulse, Energy
A 100 g ball is dropped from a height of h = 2.00 m above the
floor. Itrebounds vertically to a height of h'= 1.50 m after
colliding with the floor. Find the momentum of the ball immediately
before it collides with the floorand immediately after it rebounds.
Determine the average force exerted by the floor on the ball.
Assume that thetime interval of the collision is 0.01 seconds. How
about a collision? Consider 2 objects speedingtoward each other.
When theycollide...... Due to Newtons 3rd Law theFORCE they exert
on each otherare EQUAL and OPPOSITE. The TIMES of impact are
alsoequal. Therefore, the IMPULSES of the 2objects colliding are
also EQUAL How about a collision? If the Impulses are equalthen the
MOMENTUMSare also equal! Momentum is conserved! The Law of
Conservation of Momentum: In the absence ofan external force
(gravity, friction), the total momentumbefore the collision is
equal to the total momentum afterthe collision. Several Types of
collisions
Sometimes objects stick together or blow apart. In this
case,momentum is ALWAYS conserved. When 2 objects collide and DONT
stick When 2 objects collide and stick together When 1 object
breaks into 2 objects Elastic Collision = Kinetic Energy is
Conserved Inelastic Collision = Kinetic Energy is NOT Conserved
Example A bird perched on an 8.00 cm tall swing has amass of 52.0
g, and the base of the swing has amass of 153 g. Assume that the
swing and birdare originally at rest and that the bird takes
offhorizontally at 2.00 m/s. If the base can swingfreely (without
friction) around the pivot, howhigh will the base of the swing rise
above itsoriginal level? m/s 0.024 m 2D Collision How is momentum
conserved in 2D?
The law of conservation ofmomentum holds for allisolated, closed
systems. This is true regardless of thedirection of travel for
theobjects involved in thecollision. Collisions in 2
Dimensions
The figure to the left shows acollision between two puckson an air
hockey table. Puck Ahas a mass of kg and ismoving along the x-axis
with avelocity of +5.5 m/s. It makesa collision with puck B,
whichhas a mass of kg and isinitially at rest. The collision isNOT
head on. After thecollision, the two pucks flyapart with angles
shown in thedrawing. Calculate the speedsof the pucks after the
collision. vA vB Collisions in 2 dimensions
vA vB Collisions in 2 dimensions Graphing The force is the time
derivative of momentum.
The impulse can be found by integrating under the curve of a Force
vs. Time graph