Unit 1: Momentum and Impulse

    Unit is heavily based in kinematics and dynamics

Momentum: the difficulty to change an object’s motion; a vector quantity 

• P→=mv→ 

• kg*m/s

• deltaP = Pf-Pi 

  • mvf-mvi = m(vf-vi) = m(delta)v→ = J 

Impulse: a net force applied over a period of time; a vector quantity 

• J→ = Fnet→t = m(delta)v→

• kg*m/s or Ns

• Impulse = area under force-time graph 

Maximum Velocity 

• Vf = Ft/m 

• apply the largest net force for the longest time 

  • Vf proportionate Ft

• have the smallest mass 

  • Vf proportionate 1/m 

Cushioning 

• F = mv/t 

• increase the time to decrease the force 

  • F proportionate 1/t

• impulse (mv) is unaffected by cushioning 

Conversion of Momentum (1 dimensional) 

• momentum is conserved for collisions and explosions only if the system is isolated, meaning that the net external force on the entire system must be zero. 

• if momentum is conserved, the total momentum remains constant 

• Pt=Pt’ 

  • types of interactions 

    • collision: hit and bounce 

      • Pi1+Pi2 = Pf1+Pf2 

    • collision: objects stick together 

      • Pi1+Pi2 = Pf12

      • Pi1 +Pi2 = Vf(m1+m2) 

    • explosion (recoil): initially at rest→explode into two

      • 0=Pf1+Pf2