CHAPTER 8 MOMENTUM

to extend time and decrease force what do you do when jumping from an elevated position how much is force decreased to

bend knees so it can go back to original shape decreases force by 10 to 20 times

IMPULSE (WHAT FACTORS DOES IT DEPEND ON) (FORMULA)

change in momentum the force and the length of time that it acts on and object Impulse= Ft

what are the two most powerful tools of mechanics?

conservation of momentum conservation of energy

elastic collisions

end result= objects colliding are separate without being permanently deformed and without generating heat' net momentum (before collision) = net momentum (after collision) (momentum 1)+(momentum 2)= (momentum 1)+(momentum 2)

to extend time and decrease force what do you do when catching the ball

extend hand and catch it then cradle it

if you want to decrease impact in impulse what do you do?

extend the time

to change the momentum of something what type of impulse should it be

external because for example if you want the basketball to move it wont move by itself without an external force, since the forces come in balanced pairs that cancel in project

WHAT ARE FACTORS THAT AFFECT MOMENTUM

mass speed can have a large momentum if it has a large mass or speed or both

WHAT IS MOMENTUM

mass in motion mass x velocity

in real life are perfect collisions common + explanation + examples are perfectly elastic collisions common?

no it will be before and just right after collision however external forces will ruin that perfect collision some time after collision billiard balls after colliding experience friction with table and air that slows down momentum in space an example of perfect collisions being ruined is by gravity no

increasing impulse

optimally you want to increase both time and force or either of those factors

decreasing momentum why would you choose having a car hit the stack of hay instead of a concrete wall.

the car is stopped by the same impulse, but remember the same impulse means the same product of force and time, not the quantities of it. sooo, you would hit the hay of stack because time would be greater thus decreasing the amount of impact or force.

if time is extended 100 times the force of impact is reduced by how much?

100 times

CHANGE IN MOMENTUM (FACTORS THAT COULD MAKE IT CHANGE) (WHAT IS THE MOST COMMON CASE FOR CHANGE IN MOMENTUM) (RELATIONSHIP BETWEEN FORCE AND CHANGE IN MOMENTUM)

Velocity or mass Usually velocity Since, momentum usually changes due to velocity, it accelerates. Force produces an acceleration, so the greater the force the more it accelerates, thus the greater change in momentum.

examples of the law of conservation of momentum

atomic nuclei undergoing radioactive decay cars colliding stars exploding

why is the cannon cannon ball system net force zero before and after launching zero?

the force causing it to recoil is equal and opposite to the recoil newton's third law for every reaction there must be and opposite and equal force also the forces applied to the system are internal

IMPULSE MOMENTUM RELATIONSHIP

the greater the impulse exerted on an object, the greater change in momentum impulse=change in momentum

if there are no external forces then..

there is no impulse, thus no change in momentum

what does conserved mean

when any quantity in physics does not change

inelastic collisions

when collisions are permanently deformed and produce heat end result= objects are stuck together net momentum (before collision) = net momentum (after collision) (momentum 1)+(momentum 2)= (total mass)(velocity)

what is true about the vector sum of momenta in a collision

when objects are in momentum and split in half, the two halves have the same momentum before it split

when are collisions an example of the law of conservation of momentum

when objects collide in absence of external forces, then the net momentum of both objects before the collision equal net momentum of both objects after collision net momentum (before collision) = net momentum (after collision)

law of conservation of momentum

when there are no external forces, the momentum of a system remains unchanged.

are impulses greater when an object bounces why

yes because there are two impulses one to bring it to stop and another to go back up

at the microscopic level are perfectly elastic collisions common

yes electrically charged particles bounce off one another without producing heat