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Analyzing Collisions

Analyzing Collisions. Section 11.2 pg. 262-265. Momentum is conserved. Kinetic energy is lost. Inelastic. Before Car 1 m=2000 kg v i =16m/s Car 2 m =2000kg v i =0. After Bumpers lock m=4000kg v f =8m/s. Inelastic. Is momentum conserved? Before: 2000kg(16m/s) + 0 = 32000kgm/s

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Analyzing Collisions

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  1. Analyzing Collisions Section 11.2 pg. 262-265

  2. Momentum is conserved. Kinetic energy is lost. Inelastic Before Car 1 m=2000 kg vi=16m/s Car 2 m =2000kg vi=0 After Bumpers lock m=4000kg vf=8m/s

  3. Inelastic Is momentum conserved? Before: 2000kg(16m/s) + 0 = 32000kgm/s After: 4000kg(8m/s) = 32000kgm/s YES! Is energy conserved? Before: ½(2000kg)(16m/s)2 +0 =256 000J After: ½(4000kg)(8m/s)2 = 128 000J 128 000J – 256 000J = -128 000J NO it was lost!

  4. Elastic • Momentum is conserved. • Kinetic energy is conserved. Before Car 1 m=2000 kg vi=16m/s Car 2 m =2000kg vi=0 After Car 1 m=2000 kg v f =0 m/s Car 2 m =2000kg vf =16 m/s

  5. Elastic Is momentum conserved? Before: 2000kg(16m/s) + 0 = 32000kgm/s After: 0 + 2000kg(16m/s)= 32000kgm/s YES! Is energy conserved? Before: ½(2000kg)(16m/s)2 +0 =256 000J After: 0 + ½(2000kg)(16m/s)2 = 256 000J YES!

  6. Practice Problem A 6500 kg freight car traveling at 2.5 m/s collides with an 8000 kg stationary freight car. They interlock upon colliding. What is the kinetic energy before and after the collision? pB : (6500 kg)(2.5 m/s) = 16250 kgm/s Velocity after: 16250kgm/s = (14500)v, v = 1.12 m/s Before: ½ (6500 kg)(2.5 m/s)2 + 0 = 20313 J After: ½ (14500 kg)(1.12 m/s)2 = 9094 J Inelastic or Elastic?

  7. Practice Problem #2 Two lab carts are pushed together with a spring compressed btwn. them. Upon, release, the 5.0 kg cart repels one way with a velocity of 0.12 m/s while the 2.0 kg cart goes in the opposite direction. Find the velocity of the second car after the collision, and the kinetic energy before and after the collision: V: 0 = (5kg)(.12m/s) + (2kg)(-v), v = 3.3 m/s Before: k = 0 After: ½ (5 kg)(.12m/s)2 + ½(2kg)(3.3 m/s)2 = 11 J Elastic or Inelastic?

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