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## Vocabulary Quiz-Friday

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**How difficult is it to get something to change its momentum?****P=mv**What could be manipulated in order to change the football player’s momentum? • Brick wall? • Dinosaur eating football player?**P=mv**A change in momentum would mean a change in either the mass or velocity. We’ll always assume the velocity changes. What causes a change in velocity? a Force**Impulsealso known as change in momentum**Impulse= (force)(time) = FΔt Unit is Newton-second N-s**Increasing Momentum“Follow through” in sports**• Apply the greatest force possible for the longest time possible Impulse= (force)(time) = FΔt**Decreasing Momentum**• http://www.hailstate.com//mediaPortal/player.dbml?DB_OEM_ID=16800&id=661846&db_oem_id=16800**Decreasing Momentum**The change in momentum may be b/c of a small force exerted over a long time The change in momentum may be b/c of a large force exerted for a short time**Decreasing Momentum**To minimize the effect of the force on an object involved in a collision, the time must be increased.**Other examples that decrease the force by increasing the**time • Air bags • Catching a baseball with a glove • Fighting with padded gloves v. bare fists • Rolling with a punch Padded dashboards • Packing materials • Crumple zones • New seat belts**Practical application**Observe that the greater the time over which the collision occurs, the smaller the force acting upon the object.**Cradling the ball**• A water balloon is thrown high into the air and successfully caught. The key to the success is to contact the balloon with outstretched arms and carry the balloon for a meter or more before finally stopping its momentum. The effect of this strategy is to extend the time over which the collision occurred and so reduce the force. • This same strategy is used by lacrosse players when catching the ball. The ball is "cradled" when caught;**Other examples where extending your time decreases the force**• Bungee jumping • Bending your knees when you jump, not locking them • Safety nets/ giant air mattresses (during fires, circuses)**Impulse Activity**• Monday it is supposed to be 80 degrees • Good Luck!