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