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Impulse and Momentum

Impulse and Momentum. Newton’s third law not mentioned in energy treatment reason: gives rise to another conservation principle Ex. Explosion of object into 2 unequal masses (use to show via Newton’s Laws) to get statement of Momentum Conservation Momentum = mass * velocity [vector]

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Impulse and Momentum

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  1. Impulse and Momentum • Newton’s third law not mentioned in energy treatment reason: gives rise to another conservation principle Ex. Explosion of object into 2 unequal masses (use to show via Newton’s Laws) to get statement of Momentum Conservation • Momentum = mass * velocity [vector] • Impulse = force * time interval

  2. Examples of Impulse • Baseball : barehanded vs. glove • Boxing : bare-knuckle vs. glove • “Rolling with punch” • 1941 Chevy dashboard • Gym mats

  3. Impulse : Airplane and Bird • Bird : mass = 0.5 kg and length = 20 cm • Airplane: speed = 300 m/s = 650 mi/hr • Impulse = F∆t = ∆mv = (0.5 kg)(300 m/s) ∆t = ∆s/v = (0.20m)/(300m/s) = 6.7 * 10 - 4 s F = (150)/(6.7 * 10 – 4) = 2 * 105 N ≈ 20 tons! Cite: B-1B Bomber (stealth); Israeli Combat Jet

  4. Conservation of Momentum: • Total momentum of a system is not changed if there are no external forces. Vector Statement • Applications • Explosions: guns, cannons (fort in western Pa), buccaneers, tanks, and Hollywood. • Collisions (extremes) A. Complete Inelastic – Momentum conserved, energy lost; objects collide and stick together moving as one after collision. Ex. Football, trains, traffic accidents, and ballistic pendulum.

  5. B. Complete Elastic – Energy and Momentum conserved; objects collide and rebound (separate) with no energy lost. Ex. Pool table or marbles *** Look at 2-Dimensional Examples***

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