100 likes | 126 Views
Impulse-Momentum Theorem. Or Don’t get Stressed. Momentum. Mass times velocity of object ( p =m v ) Inertia of motion Vector quantity Units include kg m/s, g cm/s, N s Conserved quantity in collisions and explosions and cases where there is no outside force. Check Question 1.
E N D
Impulse-Momentum Theorem Or Don’t get Stressed
Momentum • Mass times velocity of object (p=mv) • Inertia of motion • Vector quantity • Units include kg m/s, g cm/s, N s • Conserved quantity in collisions and explosions and cases where there is no outside force
Check Question 1 Under which of the following circumstances will a roller skate have the same momentum as a Mack Truck? • Roller skate moves fast, truck moves slow • Truck moves fast, roller skate moves slow • Truck and roller skate move at same speed
Impulse and Impulse Momentum Theorem • An outside force that causes a change in momentum. • Internal vs. external forces • This is the same relationship that force has with velocity • Impulse = Force applied x time applied (J=F avg Dt) • Vector quantity w/ units same as momentum • J=Favg Dt=Dp = mvf - mvi
Large force over short time High stress on object Large amount of deformation Examples Small force over long time Low stress on object Small amount of deformation Examples Two Methods of Getting the Same Momentum Change
Check Question 2 • Which is a better surface to roller skate on in case of a fall, a wood or concrete rink? • What are the advantages and disadvantages of astro-turf over natural grass as a surface for a sporting event?
Momentum Changes in Elastic and Inelastic Collisions • Definition of elastic and inelastic collisions • Greater momentum transfer in bouncing or elastic collision. • Pelton’s Wheel and very sad story
Check Question 3 Use the idea of momentum to explain why an ice ball hurts more when it hits you than a snow ball. a) the mass is larger for the ice ball b) the snow ball requires a greater momentum change c) the ice ball requires a greater momentum change
The Egg Demo • Sheet allows for momentum to be changed by small force exerted over long time causing little stress on the egg. • Keep in mind when designing project. • Red Ribbon Week Demo
Changing Momentum • Hit with as great a force as possible • Extend time force is applied • Examples • Tennis, golf and baseball exert large force over long time by following through • Bow and Arrow