Momentum

• Newtons third law says that for every action there is an equal and opposite reaction.
• Equilibrium is when objects are in a state of rest or uniform motion(not accelerating)
• Equilibrium example: a book on table

  • Book push down on table and table push up on book
  • The upward force is equal and opposite to books weight
  • The resultant force on book is 0 and book stays still
• When 2 objects collide they exert equal and opposite force on each other
• Momentum is property of objects moving and how hard it is to stop them.
• Momentum(kgm/s) = mass(kg) × velocity(m/s)
• P = m × v
• Total momentum before = total momentum after
• The force acting on the objects can change momentum
• Force(N) = change in momentum(kgm/s) ÷ time(s)
• Force is equal to rate of change of momentum

  This means if you increase time taken for colliwion you reduce the force
• Large deceleration(car stops suddenly velocity changes to 0)

  • Can break bones
  • Safety features like crumple zones, air bags, seat belts
• Safety features reduce danger caused by large deceleration by increasing time taken for passengers to stop moving. This decreases deceleration and increases force on them
• If an object has more kinetic energy it will have greater momentum
• Increasing mass reduces acceleration (deceleration) so less dangerous
• Ig you increase time taken for collision you reduce forcr
• Forces acting on objects itc changes its momentum

  force= change in momehtum/time
• Safety features on cars increase time taken for passengers to stop moving which decreases their deceleration which therefore decreases te force on them