Chapter 9 Notes-Impulse and Momentum:

9.1-Momentum and Impulse:

-collision- a short-duration interaction between two objects
-the duration of a collision depends on the materials from which the objects are made (normally about 1 to 10ms (0.001 to 0.010s))
-the harder the objects, the shorter the contact time
-the forces are an action/reaction pair and have equal magnitudes =
-the force increases rapidly as the bonds compress, reaches maximum at the instant A is at rest (point of maximum compression), then decreases as the bonds re-expand

-impulsive force- a large force exerted for a small interval of time
-always grows to a maximum and then decreases back to zero
-a function of time, so we write it as:
- both and are components of vectors so they have signs indicating which way the vectors point
-we use Newton’s second law to find the final velocity; acceleration is the derivative of velocity so the second law is:
- multiply both sides by dt (9.1):
-velocity changes from to during the collision (9.2):

Momentum:

-momentum = p mv (9.3)
-momentum is a vector; units kg m/s
-the momentum vector is parallel to the velocity vector
- like any other vector can be decomposed into x and y-components:
- an object can have a large momentum by having either a small mass but large velocity or a small velocity but a large mass
- momentum is negative for a particles moving to the left or down
- (9.4):
-force is the rate of change of momentum- allows for the possibility that the mass of the object might change
- the