2Momentum and Sports"Going into the all-star break, the Chicago White Sox have the momentum.""Chicago Bears Gaining Momentum.""You have the momentum; the critical need is that you use that momentum and bury them in this third quarter." – A quote from a coach trying to pump up his team!!What do all these phrases have in common?MOMENTUM
3Momentum is commonly used in sports. A team that has the momentum is on the moveand is going to take someeffort to stop.Momentum refers to thequantity of motion that anobject has.A sports team which is "on the move" has the momentum.An object in motion ("on the move") then has momentum.
4What is Momentum? Momentum can be defined as “mass in motion.” All objects have mass; so ifan object is moving, then it hasmomentum - it has itsMASS IN MOTION.The amount of momentum whichan object has is dependent upon two variables…Mass and VelocityIn other words, how much stuff is moving and how fast the stuff is moving
6Equation Momentum = mass * velocity p=m*v Units?? kgm/sWhat is the momentum of a 60-kg halfback moving eastward at 9 m/s?p=(60kg)(9m/s)p=540kgm/s
7p=mvThe equation illustrates that momentum is directly proportional to an object's mass and to the object's velocity.An object has a large momentum if it has a large mass or a large velocity, and both variables are of equal importance in determining the momentum of an object.
8EXAMPLEConsider a Mack truck and a roller skate moving down the street at the same speed.Which will have a greater momentum?The considerably greater mass of the Mack truck gives it a considerably greater momentumConsider that the same Mack truck is at rest, but the roller skate is moving.The roller skate.Anything at rest has a momentum of “0”.It is not an “mass in motion.”
9Impulse To stop such an object, it is necessary to apply a… ForceAGAINSTTo stop such an object, it is necessary to apply a force against its motion for a given period of time
10The more momentuman object has, the harderthat is to stopIt would require agreater amount of forceor a longer amount of time(or both) to bring an objectwith more momentum to a halt.
11This is called an impulse Impulse=change in momentumor Ft=Δmv
12ESPN Video Questions1. Explain why the goal posts have padding around their base.The padding will increase the time required to stop and decrease the force.
132. A 90 kg football player is moving at 7m/s 2. A 90 kg football player is moving at 7m/s. Calculate the force required to stop him in .4 seconds; in .2 seconds; in .1 seconds.Ft=ΔmvF= Δmv/tF=(90)(7)/(.4)F=1575N
143. Examine the inside of a football helmet 3. Examine the inside of a football helmet. How is the helmet constructed so that the player’s head will have more time to stop during a collision? Why do we want to give the head more time to stop?There is space in the interior of the helmet for the head to move, thereby increasing the time.
154. List safety features in cars which lengthen the time during a collision in order to decrease the maximum force during that collision.