Dynamics

• What is mass?

  Mass is the property of a body that resists change in motion. It is also the amount of matter in an object.
• What is force?

  Force is defined as the rate of change of momentum
• What is F=ma derived from?


  (mv-mu)/t=F
• What is linear momentum?

  The linear momentum of a body is defined as the product of its mass and velocity
• What is the equation for momentum?

  p=mv
• What is Newton's first law of motion?

  A body stays at rest, or continues to move at constant velocity unless a resultant force acts on that body.
• What is Newton's second law of motion?


  The rate of change of momentum of a body is disproportional to the resultant force applied and takes place in the direction of the force.
• How is Newton's second law summarised?

  Force = rate of change of momentum
• What is Newton's third Law of motion?

  Whenever a force acts on a body, equal but oppositely directed force of the same kind acts on another body.
• What is implicit in Newton's third law of motion?

  The assumption that:- Forces occur in pairs- are of the same type- are of equal magnitude- act along the same line- act on different bodies
• What is weight?

  The effect of a gravitational field on a mass
• What is the weight of a body equal to?

  The weight of a body is equal to the product of its mass and the acceleration of free fall.
• Describe the motion of an object falling in a uniform field with air resistance


  At first, an object accelerates freely. Then increasing air resistance opposes their fall and their acceleration decreases. Eventually they reach a maximum velocity, known as the terminal velocity. At the terminal velocity the air resistance is equal to the weight.
• What does terminal velocity depend on?

  The weight and surface area of an object
• What is the principle of conservation of momentum?

  The momentum of an isolated system remains constant
• What is a perfectly elastic collision?

  In a perfectly elastic collision, relative speed of approach = relative speed of separation.
• What is conserved in a perfectly elastic collision?

  Momentum and kinetic energy
• What is an inelastic collision?

  In an inelastic collision, momentum is conserved but not kinetic energy
• Why is kinetic energy not conserved in inelastic collisions?

  It is often transformed into to different forms of energy such as heat and sound energy