Momentum: Unit 5

What is Momentum?  Momentum: ___________ in motion  Momentum= Mass x Velocity  ____________ = Mass x Speed – when direction is not an important factor  Unit: kg x m/s  The more __________ an object has, the more __________ there is possible.  Speed affects the momentum of an object.  EX. A fast car can have more momentum than a slow truck w/ greater mass  Non-moving objects have no momentum at all.

Impulse Changes Momentum  If ____________ changes, then either mass or velocity or both has changed.  If mass is unchanged and the ___________ changes then acceleration results.  Accelerations are produced by Forces.  The greater the force= ______ an objects change in velocity = Greater change in momentum.

Impulse  The quantity force X time interval = Impulse  F(delta t) = Impulse  The greater the impulse on an object, the greater the _____________ in momentum  Impulse = _____________ in Momentum  Impulse = Ft = delta (mv)  t is the time interval (delta t)  Unit = Ns

Increasing Momentum  Apply greatest force possible for as long as possible.  EX. Baseball player and Golfer swinging as hard as possible and following through with their swings.  Forces involved in impulses usually vary from ________ to instant.  EX. The force is zero on a golf ball until it is struck by the club; then the force increases rapidly as the ball’s shape becomes distorted. The force decreases as the ball returns to its original shape and increases in speed  _________________= Avg. force of impact measured in Newtons  __________________ = Impact Force x time measured in Newton seconds

Decreasing Momentum  The same impulse decreases your momentum whether hitting a wall or haystack  The same impulse does ______ mean with the same force or time.  The product of the force and time are the same- not necessarily the force and time.  Impact time is ______________ when you hit the haystack rather than the wall.  Impact time = the time during which your momentum is brought to _________.  The ___________ the impact time = reduction in force of impact = reduction in deceleration

Examples  EX of things that increase impact time and therefore decrease impact force  Airbags  Padded dashboard v. rigid dashboard  Bending your knees when you jump from an elevated position  Relaxing your body when you fall to spread force of impact over more muscles  Falling on a soft mat vs. hard floor  Moving away from a punch  EX. Increasing the time of impact 100 times reduces force of impact 100 times.  Impact force and impact time are ___________ proportional.(Two variables that affect impulse)

Conservation of Momentum  To accelerate an object, a ______ force must be applied to the object.  To change the momentum of an object, you must __________ an impulse on it.  If no net force or net impulse acts on a system, the __________ of that system cannot change.  The Law of Conservation of Momentum: In the absence of an external force, the momentum of a system remains unchanged.

Elastic Collisions  Elastic Collisions: When objects collide ___________ being permanently deformed and without generating heat.  Perfectly elastic collisions are not common in the everyday world- some __________ is produced in the collisions.

Inelastic Collisions  Inelastic Collisions: objects collide and become __________ or ___________ together generating heat and becoming ____________ in the process.  Most collisions usually involve some ______________ force.