Terminal Velocity and Momentum

• Terminal Velocity


  . When an object falls through a fluid:

  - At first, the object accelerates due to the force of gravity

  - As it speeds up, the resistive forces increase

  - The resultant force reaches zero when the resistive forces balance the force of gravity. At this point the object will fall at a steady speed, called its terminal velocity

  . Near the Earth's surface, the acceleration due to gravity is 10m/s(2)
• Newton's Third Law


  . Newton's third law is often stated as: for every action there is an equal and opposite reaction

  . This means that whenever one object exerts a force on another, the other object exerts a force back

  . This reaction force is the same type and is equal in size but opposite in direction
• Momentum


  All moving objects have momentum
• Momentum


  • The momentum of a moving object depends on its mass and its velocity
  • The greater the momentum of an object, the greater the force needed to stop the object
  • At the same speed, a large mass will have more momentum than a small mass
  • With the same mass, a faster object will have more momentum than a slower object
• Calculating momentum


  1. momentum = mass x velocity

  2. p=mv
• Momentum (p)


  Measured in kilograms metres per second (kg m/s)
• Mass (m)


  Measured in kilograms (kg)
• Velocity (v)


  Measured in metres per second(m/s)
• Conservation of Momentum

  . In a closed system, the total momentum before an event is equal to the total momentum after the event

  . This conservation of momentum is most often referred to during collisions, but also applies to rockets and projectiles

  . With rockets, the momentum gained by the exhaust being expelled backwards is equal to the momentum gained by the rocket moving forwards

  . With projectiles, the recoil momentum of the gun is equal to the momentum of the bullet